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ANALYSIS  OF  PAINT  AND 
VARNISH  PRODUCTS 


BY 
CLIFFORD    DYER    HOLLEY,    M.S.,    PH.D. 

CHIEF  CHEMIST  ACME  WHITE  LEAD  AND  COLOR  WORKS 


FIRST   EDITION 

FIRST    THOUSAND 


NEW  YORK 
JOHN    WILEY    &    SONS 

LONDON:    CHAPMAN  &  HALL,  LIMITED 
1912 


COPYRIGHT,  1912, 

BY 
CLIFFORD   DYER    HOLLEY 


Stanbopc  jprcss 

F.    H.  GILSON   COMPANY 
BOSTON,  U.S.A. 


PREFACE. 


AN  extended  experience  in  the  mixed  paint  industry 
and  in  the  manufacture  of  white  lead  and  other  lead 
products  has  convinced  the  author  that  there  is  need 
of  a  more  comprehensive  work  on  the  analysis  and  val- 
uation of  paint  products  than  has  hitherto  appeared. 

The  enactment  of  various  laws  regulating  the  sale 
of  prepared  paints  and  the  discussions  arising  there- 
from have  done  much  to  stimulate  chemical  analysis 
and  research  work  with  the  various  paint  products. 
New  combinations  have  been  brought  to  the  attention 
of  the  consumer,  who  must  rely  on  the  chemist,  official 
or  .private,  for  their  valuation  and  suitability  for  use. 
The  rapid  development  of  the  industry  and  the  in- 
creasing sharpness  of  competition  has  placed  an  added 
responsibility  upon  the  paint  chemist  of  to-day;  his 
methods  must  not  only  be  accurate,  but  must  also  be 
capable  of  securing  results  with  the  greatest  possible 
rapidity. 

It  has  been  the  endeavor  of  the  author  to  present  in 
this  volume  such  methods  as  he  has  found  accurate 
and  at  the  same  time  rapid  and  convenient.  A  con- 
siderable number  of  the  methods  are  substantially  the 
same  as  those  given  in  his  earlier  work,  "  Analysis  of 
Mixed  Paints,  Color  Pigments,  and  Varnishes."  The 
scope  of  the  work  has,  however,  been  greatly  enlarged, 
a  large  number  of  new  methods  have  been  introduced, 
with  many  new  paint  products,  whose  properties  are 
discussed,  while  a  large  amount  of  data  relative  to  the 

263608 


vi  PREFACE. 

composition  of  the  various  paint  specialties  to  be  found 
on  the  market,  has  been  included. 

The  author  wishes  to  express  his  appreciation  for 
the  assistance  given  him  by  his  many  friends  in  the 
preparation  of  this  work. 

CLIFFORD  D.  HOLLEY 

DETROIT,  MICHIGAN, 
April  12,  1911. 


CONTENTS 

PAGB 
INTRODUCTORY    CHAPTER.     THE    PROPER   LABELING   OF   PAINT 

PRODUCTS 1 

CHAP. 

I.  SEPARATION  OF  VEHICLE  FROM  PIGMENT 4 

II.  ESTIMATION  OF  WATER  IN  PAINTS 11 

III.  WATER  EMULSIONS  AND  EMULSIFIERS 17 

IV.  ESTIMATION  OF  LINSEED  OIL  AND  ITS  ADULTERATION 

IN  MIXED  PAINTS 23 

V-.   DETERMINATION  OF  THE  PURITY  OF  LINSEED  OIL  ...  32 
VI.   DETERMINATION  OF  THE  PURITY  OF  LINSEED  OIL  (Con- 
tinued)    42 

VII.  ANALYSIS  OF  THE  VOLATILE  OILS 51 

VIII.  TURPENTINE  THINNERS 59 

IX.   TURPENTINE  SUBSTITUTES 72 

X.   THE  INERT  PIGMENTS 77 

XI.   ANALYSIS  OF  WHITE  LEAD 92 

XII.  ANALYSIS  OF  SUBLIMED  WHITE  LEAD  AND  THE  ZINC 

PIGMENTS 104 

XIII.  ANALYSIS  OF  SUBLIMED  WHITE  LEAD  AND  THE  ZINC 

PIGMENTS  (Continued) 116 

XIV.  DETERMINATION  OF  FINENESS,  COVERING  POWER  AND 

TINTING  STRENGTH  OF  PIGMENTS 124 

XV.  THE  PRACTICAL  TESTING  Our  OF  PAINTS 129 

XVI.  ANALYSIS  OF  WHITE  PAINTS 143 

XVII.   ANALYSIS  OF  WHITE  PAINTS  (Continued) 153 

XVIII.   KALSOMINE,  COLD  WATER  PAINTS  AND  FLAT  WALL 

FINISHES. 163 

XIX.   COMPOSITION  OF  COLORED  PAINTS 170 

vii 


viii  CONTENTS 

CHAP.  PAGE 
XX.  ANALYSIS  OF  INDIAN  REDS,  VENETIAN  REDS,  TUSCAN 

REDS,  RED  OXIDES  AND  OCHRES 175 

XXI.  ANALYSIS  OF  BLACK  PIGMENTS  AND  PAINTS 185 

XXII.   ANALYSIS  OF  BROWN  PIGMENTS  AND  PAINTS 196 

XXIII.  ANALYSIS  OF  BLUE  PIGMENTS  AND  PAINTS 204 

XXIV.  ANALYSIS  OF  YELLOW,   ORANGE  AND  RED  CHROME 

LEADS,  ANALYSIS  OF  VERMILIONS 211 

XXV.  ANALYSIS    OF    RED    LEAD,    ORANGE    MINERAL    AND 

LITHARGE 221 

XXVI.  ANALYSIS    OF     PAINTS    FOR    MANUFACTURING    PUR- 
POSES   227 

XXVII.   COMPOSITION  AND  ANALYSIS  OF  FILLERS 233 

XXVIII.    SHINGLE  STAINS,  BARN  AND  ROOF  PAINTS 236 

XXIX.  ANALYSIS  OF  JAPANS  AND  DRIERS 239 

XXX.   ANALYSIS  OF  SHELLAC  AND  SPIRIT  VARNISHES 245 

XXXI.  ANALYSIS  OF  OIL  VARNISHES 257 

XXXII.   THE  PRACTICAL  TESTING  OF  VARNISHES 269 

XXXIII.  VARNISH  STAINS  AND  COLOR  VARNISHES 279 

XXXIV.  ENAMELS  AND  VARNISH  SPECIALTIES.  .  282 


ANALYSIS  OF 
PAINT  AND  VARNISH  PRODUCTS 


INTRODUCTORY  CHAPTER. 

THE  PROPER  LABELING  OF  PAINT  PRODUCTS. 

1.  Let  the  label  tell  the  truth.    It   is  indeed   unfor- 
tunate that  large  quantities  of  ready-mixed  and  paste 
paints  are  sold  to-day  more  on  the  strength  of  the 
vigorous  advertising  conducted  by  the  manufacturers 
than  on  the  merit  of  the  products  themselves.     The 
extravagant  claims  of  the  manufacturers  and  the  many 
instances  of  detected  fraud  have  aroused  the  consumer 
to  the  need  of  adequate  protection.     To  this  end  nu- 
merous state  paint  laws  have  been  enacted  requiring 
the  composition  of  each  paint  product  of  whatever 
description  to  be  printed  on  the  label.     This  procedure 
has  been  met  with  vigorous  opposition  on  the  part  of 
the  paint  manufacturers,  who  claim  that  they  are  thus 
compelled  to  reveal  valuable  trade  secrets.     Such,  how- 
ever, is  not  the  case,  as  in  no  instance  has  it  been  found 
necessary  to  place  on  the  label,  in  order  to  comply 
with  the  various  laws,  any  information  but  that  which 
a  competent  chemist  could  ascertain  with  ease. 

2.  Fraud    confined   to    certain    classes   of    paints.     A 
careful  examination  of  the  situation  will  show  that 
fraud  and  abuse  have  been  confined  almost  without 
exception  to  white  leads  so  called,  paste  paints,  and 
ready-mixed  house  and  barn  paints;  in  other  words,  to 

1 


2  ^         PAINJ.AND  VARNISH  PRODUCTS. 

paint  products  in  which  varnish  is  not  an  essential 
constituent.  The  various  paint  specialties,  such  as  car- 
riage paints,  enamel  paints  for  various  purposes,  etc., 
are  of  such  a  nature  that  the  manufacturer  cannot 
afford  to  take  chances  in  exploiting  an  inferior  article, 
and  he  must  manufacture,  if  he  desires  to  be  successful, 
as  good  a  product  as  he  can  for  the  price  for  which  he 
sells  it. 

It  therefore  seems  unwise  to  surround  with  rigid 
regulations  a  class  of  products  with  which  no  fraud 
has  been  practiced  and  which  is  not  readily  susceptible 
to  fraudulent  practice.  It  is  only  reasonable  to  be- 
lieve that  the  lawmakers  desired  to  regulate  the  sale  of 
such  paint  products  as  they  were  acquainted  with  and 
which  are  the  more  common  ones  in  everyday  use;  and 
to  require  labeling  as  to  composition  of  paints  contain- 
ing varnish  as  an  essential  constituent  is  going  a  step 
beyond  the  possibility  of  practical  enforcement  and  at 
the  same  time  is  not  justified  by  present  conditions. 

3.  Necessity  for  labeling  mixed  paints.  The  practice 
of  labeling  a  low-priced  mixture  of  barytes,  whiting, 
and  zinc  oxide  as  strictly  pure  white  lead  and  claiming  a 
high  degree  of  wear  and  durability  for  a  mixed  paint 
containing  considerable  quantities  of  water,  a  large 
excess  of  benzine,  and  a  high  percentage  of  extenders 
like  barytes,  clay,  whiting,  etc.,  will  not  cease  until  the 
sale  of  such  products  is  regulated  by  law  and  the 
purchaser  is  given  ample  opportunity  of  knowing  just 
what  he  is  buying.  Such  combinations  may  have  a 
commercial  value,  but  the  selling  price  should  be  de- 
termined accordingly,  and  chemical  analysis  can  be 
depended  upon  to  show  their  probable  service  value. 

Valuation  of  paints  by  analysis.  It  is  indeed  probable 
that  chemical  analysis  alone  will  not  enable  the  pur- 


INTRODUCTORY  CHAPTER.  3 

chaser  to  select  the  best  wearing  paint  from  among 
several,  if  each  is  composed  of  white  lead  and  zinc 
oxide,  with  possibly  a  small  percentage  of  inert  pig- 
ments, suitably  ground  in  pure  linseed  oil,  and  a  req- 
uisite amount  of  turpentine  drier  added,  even  if  the 
percentage  of  the  different  constituents  vary  consider- 
ably. 

In  such  instances,  however,  the  analysis  will  indicate 
that  the  purchaser  is  at  least  securing  a  fair  product 
for  his  money,  and  if  properly  applied  may  be  de- 
pended upon  to  give  satisfactory  service.  Also,  if  he 
possesses  even  a  moderate  knowledge  of  the  value  of 
paint  ingredients,  the  placing  of  the  analysis  on  the 
can  will  enable  him  to  select  a  paint  the  composition 
of  which  is  most  nearly  in  accord  with  his  ideas. 

4.  Placing  an  additional  burden  on  the  manufacturer. 
Requiring  all  paint  products  to  be  labeled  as  to  com- 
position places  an  undue  burden  of  expense  upon  the 
manufacturer,  which  is  by  no  means  slight,  owing  to 
the  immense  variety  of  his  products,  each  of  which  is 
likely  to  appear  in  several  shades  or  colors.  On  the 
other  hand,  requiring  him  to  place  the  analysis  on 
paints,  whether  ready-mixed  or  in  paste  form,  in  which 
varnish  is  not  a  necessary  ingredient,  involves  a  slight 
cost  only,  and  at  the  same  time  efficiently  protects  the 
consumer. 


CHAPTER  I. 

SEPARATION  OF  VEHICLE  FROM  PIGMENT. 

5.  Preparation  of   sample.     If   a   dry   color,    and  in 
bulk,  great  care  must  be  exercised  in  securing  a  uni- 
form sample,  which  should  be  thoroughly  mixed  on 
the  mixing  cloth.     If  the  sample  be  a  liquid  paint  in 
the  unbroken  package,  the  brand,  manufacturer,  and 
guarantee,  or  other  statements  of  importance  appearing 
on  the  label,  should  be  carefully  recorded.     The  can 
should  also  be  examined  for  any  evidence  of  leakage, 
or  any  markings  indicating  the  date  of  manufacture. 
On  opening  the  package  the  unfilled  portion  should  be 

ed  by  placing  a  straightedge  across  the  top  of 
n  and  measuring  with  a  ruler  the  distance  down- 
ward to  the  surface  of  the  oil.  The  gross  weight  of 
the  package  should  also  be  recorded  at  this  time. 

6.  Condition  of  sample.      The  clear  oil  portion  should 
be  carefully  removed  wittf  the  aid  of  a  pipette  or  suction 
flask,  and  the  surface  of  the  paste  portion  remain- 
ing should  be  examined  carefully  for  evidence  of  any 
precipitation  of  the  drier  constituents,  which  will  often 
form  a  gummy  layer  on  the  surface  of  the  paste.     The 
older  the  sample  the  more  pronounced  the  precipita- 
tion.    The  condition  of  the  paste  portion  is  readily 
ascertained   with  a  steel  spatula,  and  the   degree  of 
settling,  hardening,  and  any  separation  of  the  coarser 
particles  due  to  poor  grinding,  should  be  noted. 

7.  Obtaining  a  uniform  sample.     The  paste  is  then 
completely  removed  to  a  larger  can,  known  as  the  mix- 
ing can,  which  should  be  kept  solely  for  this  purpose, 

4 


SEPARATION  OF  VEHICLE  FROM   PIGMENT. 


and  stirred  until  smooth.  The  reserved  oil  portion  is 
gradually  added,  with  constant  stirring,  which  should 
be  continued  until  the  analyst  is  thor- 
oughly convinced  that  the  sample  is 
uniform  in  composition.  The  entire  suc- 
cess of  the  analysis  depends  upon  secur- 
ing a  uniform  sample,  and  more  analyses 
are  incorrect  because  of  carelessness  in 
the  preparation  of  the  sample  to  be  an- 
alyzed than  from  any  other  source. 

8.  Weight.    The  weight  of  the  cleaned 
can  subtracted  from   the  gross  weight 
gives  the  net  weight  of  the  sample.    The 
can  is  then  filled  to  the  height  occupied 
by  the  sample,  as  noted  above,  with 
water  from  a  carefully  graduated  meas- 
ure, thus  giving  the  net  volume  of  the 
paint.     The   can  is  then  filled  to  the 
brim  with  a  measured  amount  of  water 
and  the  capacity  of  the  can  recorded. 

9.  Separation   of   the  vehicle.     Much 
difficulty  is  often  experienced  in  extract- 
ing the  vehicle  from  the  pigment,  due  to 
the  fineness  of  the  pigment  particles  and 
the  ease  with  which  they  pass  through 
the  walls  of  the  extraction  tubes.     This 
difficulty,  however,  may  be  avoided  by 
the  use  of  the  apparatus  illustrated  be- 
low.    The  extraction  thimble,  contain- 
ing a  filter  folded  cylindrically,  is  dried 
in  the  hot-water  oven  for  thirty  min- 
utes, weighed,  and  10  to  15  grams  of  the  sample  weighed 
into  it,  extracted  with  ether  for  24  to  36  hours,  dried, 
and  weighed  again.     The  loss  in  weight  represents  the 


FIG.  2. 
EXTRACTION 
APPARATUS. 


6  PAINT  AND  VARNISH  PRODUCTS. 

vehicle,  and  the  residue  remaining,  the  pigment,  which 
is  reduced  to  a  fine  powder  and  kept  tightly  stoppered 
until  examined.  Any  casein  or  similar  product  in  the 
paint  will  remain  unextracted  by  the  ether  and  unless 
detected  will  interfere  with  the  proper  analysis  of  the 
pigment.  With  very  finely  divided  pigments  like  Prus- 
sian blue  a  thickly  padded  Gooch  crucible  may  be 
used;  the  successive  extractions  may  be  decanted  into 
it,  using  a  strong  suction  and  refilling  the  Gooch  before 
it  sucks  dry. 

10.  Extraction  with  acetone.     If  the  paint  contains 
a  considerable  percentage  of  water  the  extraction  can 
be  best  accomplished  with  the  use  of  a  good  grade  of 
acetone.     Many  chemists  prefer  a  solvent  prepared  by 
mixing  50  parts  benzol,  30  parts  wood  alcohol,  and  20 
parts  refined  acetone. 

11.  Removal  of  vehicle  in  quantity.    Another  method 
of  obtaining  sufficient  vehicle  from  a  paint  for  the  de- 
termination of  the  volatile  oils,  the  quality  of  the  lin- 
seed oil,  etc.,  is  to  fill  a  tall  cylinder  with  such  of  the 
sample  as  is  not  needed  for  the  water  estimation  (100 
to   150  grams)    and  for  obtaining  the  free  pigment, 
corking  it  tightly,  and  placing  it  in  a  tall  copper  can 
filled  with  water  heated  to  about  70°  C.     By  reducing 
the  viscosity  of  the  oil  in  this  manner  the  pigment  will 
settle  quite  rapidly,  and  in  24  hours,  if  the  temperature 
is  maintained  at  70°  C.,  sufficient  oil  may  be  siphoned 
off  with  the  aid  of  the  suction  pump. 

12.  Use  of  centrifuge.     By  far  the  most  convenient 
method  of  obtaining  sufficient  vehicle  for  examination 
is  by  centrifuging  the  paint.     In  the  average  labora- 
tory an  electric  centrifuge  is  the  most  convenient  type. 
The  cylinders  used  may  be  of  glass,  but  preferably  of 
aluminum,  as  the  pressure  on  the  ends  is  often  severe 


SEPARATION  OF  VEHICLE  FROM  PIGMENT. 


when  the  centrifuge  is  in  motion.  The  bottoms  of  the 
cylinders  should  be  removable,  being  screwed  onto  the 
cylinder.  This  permits  of  the  easy  removal  of  the  pre- 
cipitated paint  and  the  rapid  cleaning  of  the  cylinders. 

13.  Balancing  the  cylinders.     It  is  necessary  that  the 
cylinders  opposite  one  another  be  evenly  balanced,  and 
it  is   always  advisable   to  balance  up   the   cylinders 
on  the  scales  before  placing  them  in  the  centrifuge. 
The  cylinders  should  be  tightly  corked  to  prevent  loss 
by  evaporation  of  the  volatile  thinners,  and  live  steam 
admitted  into  the  centrifuge  chamber  sufficient  to  heat 
the  contents  of  the  tubes  to  about  70°  C.     In  the 
majority  of  cases  the  pigment  will  be  thrown  out  rap- 
idly and  cleanly  and,  by  using  a  number  of  cylinders, 
an  ample  amount  of  the  oils  may  be  easily  obtained. 

14.  Power   centrifuges.     In  the   factory  laboratory, 
where  steam  pressure  is  always  available,  an  ordinary 
Babcock  butter-fat  test  can  be  conveniently  used,  the 
steam  leakage  into  the  upper  chamber  being  sufficient 
to  keep  the  tubes   warm   enough  to  insure  the  rapid 
precipitation  of  the  pigment.     The  machine  selected 
for  this  purpose  should  be  very  strongly  made.     One 
of  the  safest  and  most  satisfactory  centrifuges  on  the 
market  is  that  illustrated  in  this  connection  (Fig.  3), 
manufactured  by  the  International  Instrument  Com- 
pany, Cambridge,  Mass. 

15.  CENTRIFUGAL  FORCE  IN  CENTRIFUGES. 


Centrifuge  Head. 

Capacity 
of  Tubes 
in  c.c. 

Average 
Rotating 
Diameter 
in  cm. 

Force  in  Lbs.  per  Lb.  in  Revolutions 
per  Minute. 

8-place  combi- 
nation 

500 
250 
100 
50 

43 
40 
44 

38 

600 

86 
80 
88 
76 

1200 

344 
320 
352 
304 

1800 

774 
720 
792 
684 

2400 

1380 
1280 
1480 
1216 

3000 

2150 
2000 
2200 
1900 

3600 

4000 

2740 

8 


PAINT  AND  VARNISH  PRODUCTS. 


EXAMPLE  :  A  cup,  weighing  2  pounds,  at  a  speed  of 
3000  r.p.m.,  would  exert  a  stress  of  4000  Ibs.  on  its 
trunnions. 


FIG.  3. 

16.  Cushioning  of  glassware.  A  rubber  cushion 
should  be  supplied  for  each  tube.  Place  a  little  water 
in  the  metal  tube,  insert  the  glass  tube,  press  down, 
and  allow  the  water  to  overflow  the  metal  tube.  If 


SEPARATION  OF  VEHICLE  FROM   PIGMENT. 


9 


this  care  is  taken  in  the  matter  of  balancing  pressures 
and  of  cushioning  there  should  be  very  little  breakage 
of  glassware. 

17.  Rapid  separation  of  pigment.     If  only  the  pigment 
is   desired  the  separated  oil  may  be  poured  off  and 
the  precipitated  pigment  stirred  up  with  benzine,  cen- 
trifuged,  and  the  operation  repeated  once  more.    This 
will  insure  the  removal  of  practically  all  the  linseed 
oil,  only  a  trace  remaining.     When  dried  the  pigment 
should   receive   an   especially   careful   mixing,   as   the 
centrifuging  causes  the  pigments  to  settle  to  a  certain 
extent  according  to  their  specific  gravities. 

18.  Typical  analyses l  of  white  and  gray  paints  from 
the  same  manufacturers,  showing  the  change  in  the 
ratio  of  pigment  to  vehicle: 


] 

'. 

I 

I. 

I] 

[I. 

White. 

Lead 
Color. 

White. 

Gray. 

White. 

Gray. 

Pigment       

65.6 

57.2 

62.6 

54.9 

63.2 

54.9 

Vehicle     

34.4 

42.8 

37.4 

45.1 

36.8 

45.1 

Vehicle: 
Linseed  oil  

100.0 
88.9 

100.0 
89.5 

100.0 
86.0 

100.0 

84.7 

100.0 
97.0 

100.0 
83.9 

Drier     

9.3 

8.6 

12.6 

13.8 

2.0 

14.9 

Water  

1.8 

1.9 

1.4 

1.5 

1.0 

1.2 

Pigment: 
White  lead          .           .   . 

100.0 
14.65 

100.0 
14.18 

100.0 
44.08 

100.0 
27.29 

100.0 
50.52 

100.0 
33.98 

Lead  sulphate    . 

0.34 

0.27 

4.62 

4.39 

.00 

2.84 

Zinc  oxide               .       .    . 

63.42 

63.27 

41.41 

50.94 

46.06 

41.80 

Calcium  carbonate 

4  59 

7.10 

3.18 

6  94 

Silicia 

20  91 

20.14 

12.14 

Magnesium  silicate 

5  16 

6.94 

0.68 

2.14 

0.20 

3.34 

0.24 

2.30 

100.0 

100.0 

100.0 

100.0 

100.0 

100.0 

1  Analyses  by  the  author. 


10  PAINT  AND  VARNISH  PRODUCTS. 

19.  Ratio  of  pigment  to  vehicle.  It  is  customary  with 
a  large  number  of  manufacturers  to  have  one  ratio 
of  pigment  to  vehicle  for  white  paints  and  another 
ratio  for  the  tints.  In  some  cases  this  is  necessary, 
owing  to  the  low  specific  gravity  of  the  tinting  colors, 
but  in  many  instances  where  only  one  or  two  per  cent 
of  color  is  added  to  the  white  base  it  is  not  necessary 
materially  to  reduce  the  proportion  of  pigment. 


CHAPTER  II. 

ESTIMATION  OF  WATER  IN  PAINTS. 

20.  Occurrence.     A  fraction  of  1  per  cent  of  water 
may  occur  normally  in  the  vehicle.     A  small  percent- 
age,  1  to  3  per  cent,  may  be  incorporated  into  the 
paint  by  the  manufacturer  under  the  belief  that  it 
secures  better  penetration  when  applied  to  surfaces 
that  are  slightly  damp,  and  also  that  it  will  prevent 
the  pigment  from  settling  and  becoming  hard  in  the 
can.     Oftentimes,  however,  large  quantities  are  intro- 
duced for  the  purpose  of  cheapening  the  product.     The 
water  may  be  added  to  the  paint  and  prevented  from 
separating  out  by  forming  an  emulsion  with  the  oil  by 
the  aid  of  an  alkali,  or  by  grinding  it  into  the  pigment, 
using  an  adhesive,  such  as  glue  or  casein.     In  the  first 
case  the  nature  of  the  ash  left  on  burning  some  of  the 
separated  vehicle  will  indicate  whether  an  alkali  has 
been  used  or  not.     In  the  second  case  the  vehicle  will 
yield  less  than  1  per  cent  of  water  .when  distilled  with 
a  dry,  inert  substance  such  as  sublimed  lead,  as  the 
water  remains  with  the  pigment. 

21.  Detection.     Water  may   be   tested   for   qualita- 
tively in  light-colored  paints  by  rubbing  with  a  little 
eosin  on  a  glass  plate.     If  water  is  present  the  paint 
will  take  on  a  strong  pink  color,  otherwise  the  color 
will  remain  practically  unchanged.     If  the  paint  con- 
tains considerable  coloring  material,  rendering  the  eosin 
inapplicable,  a  weighed  strip  of  gelatine  may  be  im- 
mersed in  the  paint  for  several  hours.     If  water  is 
present  the  gelatine  will  soften  and  increase  in  weight, 

11 


12  PAINT  AND  VARNISH  PRODUCTS. 

the  adhering  paint  being  removed  by  the  use  of  petro- 
leum ether  and  drying  for  a  minute  or  two  between 
sheets  of  filter  paper.  An  immersion  of  the  gelatine 
for  18  to  24  hours  will  show  the  presence  of  water  in  a 
paint  containing  as  little  as  2  per  cent. 

22.  Estimation    of    water    with    amyl    reagent.      This 
method,  worked  out  by  the  author  in  his  laboratory, 
has  given  excellent  results,  not  only  in  mixed  paints 
but  also  in  paste  and  semi-paste  goods.     The  deter- 
mination requires  only  a  few  minutes,  and  as  the  com- 
bined water  of  the  white  lead  is  not  driven  off  there  is 
no  correction  to  be  applied. 

23.  Preparation  of  amyl  reagent.     This  method  has 
also  given  admirable  results  when  applied  to  the  de- 
termination of  water  in  rosin  oil  and  in  varnishes  con- 
taminated with  water.     The  components  of  the  amyl 
reagent  —  amyl  acetate  and  amyl  valerianate  —  should 
be  as  pure  as  possible,  and  unless  of  specified  purity  an 
inferior  grade  is  apt  to  be  obtained  which  will  yield 
unreliable  results.     Fritsche  Brothers,  New  York  City, 
have  furnished  the  most  satisfactory  article  the  author 
has  been  able  to  secure.     The  amyl  acetate  and  vale- 
rianate should  be  washed  before  mixing  with  at  least 
two  changes  of  pure  distilled  water  at  room  tempera- 
ture.    This  can  readily  be   accomplished  in   a  large 
separatory  funnel.     Washing  with  water  will  remove 
practically  all  the  impurities,  and  such  as  may  remain 
will  be  saturated  at  that  temperature.     The  reagent 
is  prepared  by  mixing  5  parts  of  amyl  acetate  with  1 
part  of  amyl  valerianate. 

24.  Determination.     About   100  grams  of  the   thor- 
oughly stirred  sample  of  paint  are  weighed  into  a  flat- 
bottomed,    200-250   c.c.,    side-necked   distilling   flask. 
Add  75  c.c.  of  the  amyl  reagent  and  with  a  gentle 


ESTIMATION  OF  WATER  IN  PAINTS. 


13 


rotary  motion  secure  a  thorough  mixing  of  the  contents 
of  the  flask.  Connect  with  an  upright  condenser  and 
distill  over  about  60  c.c.  of  the  reagent  into  a  cylinder 
graduated  into  tenths  of  cubic  centimeters.  When  the 
larger  portion  of  water  has  passed  over,  the  upper 
portion  of  the  flask  should  be  warmed  gently  with  the 
naked  flame,  in  order  to  expel  the  small  portion  of 
moisture  that  will  have  collected  on  the  sides  of  the 
flask.  The  distillation  should  then  be  continued  until 
the  requisite  amount  of  reagent  has  distilled  over. 
The  percentage  of  water  can  then  be  easily  read  off 
from  the  graduated  cylinder  and  the  contents  of  the 
distilling  flask  will  be  sufficiently  liquid  to  insure  easy 
removal.  With  paints  high  in  volatile  oils  the  volume 
of  the  distillate  should  be  increased  to  at  least  75  c.c. 

25.  Practical  example.  The  following  determination 
with  a  paint  of  known  water  content  indicates  the 
satisfactory  nature  and  accuracy  of  this  method. 

White  lead 115  grams 

Linseed  oil 40  grams 

Turpentine 10  grams 

Water 6  grams 

were  thoroughly  mixed,  introduced  into  a  side-necked 
distilling  flask,  75  c.c.  of  the  prepared  amyl  reagent 
added,  and  the  mixture  agitated  until  of  uniform  con- 
sistency. The  following  distillation  figures  were  ob- 
tained : 


Temperature. 

Water. 

Amyl  Reagent  and 
Turpentine. 

Deg.  C. 

c.c. 

c.c. 

92-110 

5.5 

16 

110-125 

0.9 

13 

125-140 

0.0 

18 

140-145 

0.0 

14 

6.4 

61 

14  PAINT  AND  VARNISH  PRODUCTS. 

The  same  mixture  without  the  addition  of  water  gave 
0.3  c.c.  of  water  when  run  as  a  blank. 

Theoretical  percentage  of  added  water 3.51 

Percentage  of  water  obtained  (corrected) 3 . 56 

Toluene  is  preferred  by  some  chemists  instead  of  the 
amyl  reagent;  its  use  for  this  purpose  is  not  recom- 
mended by  the  author  as  the  results  are  almost  inva- 
riably low. 

26.  Estimation  bf  water  by  distillation  with  inert  pig- 
ment.   This  method  has  found  a  wide  use  among  paint 
chemists.     It  is  best  carried  out  by  using  a  retort,  the 
neck  of  which  forms  the  inner  tube  of  a  condenser,  the 
outside  tube  being  a  Welsbach  chimney.     One  hun- 
dred grams  of  the  paint  is  weighed  into  an  aluminum 
beaker  and  mixed  with  a  thoroughly  dried,  inert  pig- 
ment like  silica  or  sublimed  lead  until  it  ceases  to  be 
pasty,  and  then  transferred  to  the  retort,  which  is 
heated  in  an  oil  bath,  the  water  being  collected  in  a 
graduate    calibrated    to    fifths   of    cubic    centimeters. 
Toward  the  end  of  the  distillation,  the  temperature  of 
the  contents  of  the  retort  being  raised  to  200°  C.,  a 
very  slow  current  of  air  or  illuminating  gas  is  admitted 
to  the  retort  through  a  tube  passing  nearly  to  the 
surface  of  the  pigment.     This  will  carry  over  the  last 
traces  of  moisture. 

27.  Use  of  illuminating  gas.     It  is  advisable  to  pass 
the  illuminating  gas  through  a  wash  bottle  containing 
sulphuric  acid,  which  not  only  serves  to  remove  mois- 
ture but  acts  as  an  indicator  for  the  rate  of  flowing 
gas.     The  heating  should  be  continued  for  at  least  two 
hours  at  the  above  temperature  to  insure  the  complete 
removal  of  the  combined  water  from  the  basic  carbo- 
nate of  lead  which  may  be  present.     This  should  be 


ESTIMATION  OF  WATER  IN   PAINTS.  15 

deducted  from  the  total  amount  of  water  obtained  by 
multiplying  the  basic  carbonate  present  by  2.3  per  cent, 
which  represents  the  average  per  cent  of  combined 
water  in  white  lead. 


FIG.  4. —  ESTIMATION  OF  WATER. 

28.  Combined  water.  It  is  impossible  to  remove  the 
combined  water  by  this  method  without  decomposing 
part  of  the  lead  hydroxide  of  the  white  lead,  as  the 
water  of.  combination  begins  to  split  off  at  110°  to 
120°  C.,  the  total  combined  water  being  driven  off  at 
150°  C.  with  6  hours  heating  with  little  or  no  loss  of 


16  PAINT  AND  VARNISH  PRODUCTS. 

carbon  dioxide.  An  exposure  of  4  hours  at  a  tempera- 
ture of  175  degrees  results  in  the  loss  of  all  the  water 
and  a  slight  amount  of  carbon  dioxide;  at  200  degrees 
an  exposure  of  2  hours  is  sufficient  to  remove  all  the 
combined  water  and  about  one-quarter  to  one-third  of 
the  carbon  dioxide. 

In  each  case  a  blank  should  be  run  in  order  to  ascer- 
tain that  the  inert  pigment  and  illuminating  gas  are 
free  from  condensible  moisture. 

The  author  believes  that  a  current  of  air  obtained  by 
the  use  of  an  aspirator  is  preferable  to  the  use  of  illu- 
minating gas,  as  with  the  latter  there  is  the  possibility 
of  the  formation  of  water  from  the  hydrogen  of  the 
illuminating  gas  and  the  lead  oxide  present,  if  the  tem- 
perature is  raised  too  high. 

29.  Analyses.  Eighty  mixed  paints  analyzed  by  the 
author,  white  and  gray  shades,  gave  a  water  content 
calculated  on  the  basis  of  total  vehicle,  as  follows: 

Amount  of  Water.  Number  of  Paints. 

0  to    1  per  cent 26 

1  to    3  per  cent 25 

3  to    6  per  cent 5 

6  to  10  per  cent 3 

10  to  24  per  cent 21 


CHAPTER  III. 

WATER  EMULSIONS  AND  EMULSIFIERS. 

30.  Occasionally  it  devolves  upon  the  paint  chemist 
to  determine  the  agents  used  for  securing  and  main- 
taining the  emulsion  of  oil  and  water  in  paints  and  for 
preventing  the  hardening  of  paste  goods,  such  as  com- 
bination leads,  etc. 

31.  Necessity  of  an  emulsion.     The  use  of  water  in 
paints  has  been  a  much  discussed  question.     The  ma- 
jority of  paint  manufacturers  have  maintained  that 
the  addition  of  a  certain,  amount  of  water  is  essential 
for  the  preparation  of  a  high-grade  paint,  in  order  to 
prevent  the  pigments  from  settling  hard  in  the  bottom 
of  the  can,  in  which  case  there  is  much  trouble  and 
difficulty  experienced  in  " breaking  up"  the  paint  when 
desired  for  use.     As  regards  this  contention  the  author 
believes  the  manufacturers  are  in  the  right,  that  better 
results  are  secured  by  the  use  of  a  small  percentage  of 
water  in  a  paint  high  in  lead  and  zinc.     The  line  of 
demarcation,  however,  between  the  amount  that  can  be 
considered  legitimate  for  this  purpose  and  that  which 
may  be  considered  as  added  for  adulteration  or  cheap- 
ening, is  by  no  means  well  defined.     The  author's  ex- 
perience has  led  him  to  believe  that  the  true  purpose 
of  the  addition  of  the  water  is  best  served  by  using  an 
amount  not  exceeding  3  per  cent  of  the  vehicle  present, 
and  that  any  amount  in  excess  of  5  per  cent  may  be 
regarded  as  having  been  added  for  cheapening  the 
product. 

17 


18  PAINT  AND  VARNISH  PRODUCTS. 

32.  Impairment  of  service  value.     The  addition  of  any 
considerable  percentage   of  water  unquestionably  re- 
duces the  service  value  of  a  paint,  but  it  is  more  often 
the  materials  used  with  the  water  to  obtain  the  emul- 
sion  that   cause   the   greater   harm.     Any   substance 
which  is  astringent  in  its  action,  or  which  will  cause  a 
partial  saponification  of  the  oil,  or  bring  about  reac- 
tions between  the  oil  and  the  pigments  present,  mate- 
rially reduces  the  wearing  value  of  such  paint,  and  the 
author  can  only  regard  the  addition  of  such  substances 
as  willful  adulteration. 

33.  Classification.     We  may  therefore  divide  the  emul- 
sifying agents  into  two  classes,  —  those  which  are  inert 
and  those  which  are  more  or  less  active. 

The  first  class  comprises  such  substances  as: 

Glue, 

Casein  (free  from  alkali), 

Oleates  of  lead  and  alumina, 

Turpentine, 

Glycerine,  and 

Starch. 

The  second  class: 

Chloride  of  lime, 
Sulphate  of  zinc, 
Silicate  of  soda, 
Carbonate  of  soda, 
Caustic  soda, 
Lead  acetate, 
Borax,  and 
Phosphate  of  soda. 

34.  Glue    and    Casein.     The    presence    of    glue    and 
casein  may  be  detected  by  heating  a   small  portion 


WATER  EMULSIONS  AND  EMULSIFIERS.  19 

of  the  pigment,  secured  by  extraction  with  ether,  in  a 
small  porcelain  crucible  and  noting  the  odor  given  off, 
and  comparing  the  same  with  that  obtained  by  heat- 
ing a  mixed  pigment  to  which  a  little  glue  or  casein 
has  been  added.  The  amount  present  may  be  deter- 
mined by  running  a  nitrogen  determination  according 
to  the  Kjeldahl  method  and  multiplying  the  nitrogen 
content  by  6.37.  About  10  grams  of  pigment  should 
be  used. 

35.  Oleate  of  lead.     Oleate  of  lead  is  but  rarely  used, 
as  it  is  the  most  expensive  of  all  emulsifiers.     The 
present    methods    for    detection   and    estimation   are 
unsatisfactory. 

36.  Turpentine.    Turpentine  is  by  far  the  best  emul- 
sifier  to  use,  as  it  is  itself  a  normal  constituent  of  paint. 
The  formation  of  a  water-turpentine  emulsion  can  best 
be  accomplished  by  grinding  into  a  paste  a  non-settling 
pigment   like  asbestine  pulp   (magnesium  silicate)  or 
china  clay  with  a  little  linseed  oil,  adding  water  and 
turpentine.     The  following  affords  a  base  of  uniform 
consistency  and  composition  which  can  be  added  to 
any  mix  of  pigments  in  any  desired  proportion : 

\  150  Ibs.  China  clay, 
150  Ibs.  asbestine  pulp, 
21  gal.  water, 
4  gal.  linseed  oil, 
2  gal.  turpentine. 

A  formula  like  the  above  possesses  much  merit,  as 
both  china  clay  and  asbestine  pulp  are  especially 
valued  for  their  non-settling  qualities  and  acting  in 
conjunction  with  the  water  will  prevent  any  reason- 
able combination  of  pigments  from  settling  hard,  even 
when  used  in  small  quantity. 


20  PAINT  AND  VARNISH  PRODUCTS. 

37.  Glycerine.     Glycerine  and  starch  are  often  used 
in  conjunction  with  each  other,  not  only  for  the  pur- 
pose of  introducing  water  but  to  prevent  the  hardening 
of  paste  goods,  such  as  combination  leads.     The  fol- 
lowing working  formula  illustrates  their  use : 

500    Ibs.  white  lead, 
300    Ibs.  zinc  oxide  "  xx," 
150    Ibs.  white  mineral  primer, 
200    Ibs.  barytes, 

2  oz.  ultramarine  blue, 
|  Ib.  glycerine, 
1    Ib.  starch  (powdered), 
15^  gal.  linseed  oil. 

38.  Chloride  of  lime.     This  product,  while  one  of  the- 
most  powerful  emulsifying  agents,  is  the  most  harm- 
ful to  use  owing  to  its  astringent  action  on  linseed  oil. 
Just  what  the  chemical  reactions  are  which  it  enters 
into  are  difficult  to  determine,  and  it  is  difficult  if  not 
impossible  to  prove  its  presence  in  the  majority  of 
paints  in  which  it  is  used  except  as  indicated  by  failure 
to  give  satisfactory  service  value. 

39.  Sulphate  of  zinc.     The  evil  effects  of  sulphate  of 
zinc  have  been   fully  discussed  by  the  writer  in  his 
work  devoted  to  Zinc  and  Lead  Pigments,  Chapters 
XVI  and  XVII;  therefore  they  need  not  be  discussed 
here. 

40.  Carbonate  of  soda  and  caustic  soda.     These  two 
substances  are  perhaps  more  generally  used  than  any 
of  the  others.     The  conversion  of  a  portion  of  the  lin- 
seed oil  into  a  water-soluble  soap  necessarily  results 
in  decreasing  the  life  or  wearing  value  of  the  paint 
in  which  the  above  ingredients  may  be  used.     Their 
presence  may  be  judged  by  incinerating  a  small  portion 
of  the  vehicle  and  examining  the  nature  of  the  ash 
obtained. 


WATER  EMULSIONS  AND  EMULSIFIERS.  21 

41.  Acetate  of  lead.    The  use  of  acetate  of  lead  as 
an  emulsifying  agent  cannot  be  commended.     It  acts 
as  an  astringent  on  the  oil,  although  its  effect  is  prob- 
ably not  so  severe  if  it  is  incorporated  into  the  paint 
subsequent  to  its  passage  through  the  mill  as  it  would 
be  if  it  were  added  in  the  original  mix.     A  warm  mill 
running  under  a  suitable  tension  will  cause  any  appre- 
ciable amount  of  acetate  of  lead  to  act  vigorously  on 
the  linseed   oil,  causing  a  more  or  less  pronounced 
hardening  in  the  package  as  well  as  diminishing  the  life 
of  the  paint. 

42.  Borax  and  phosphate  of  soda.     These  products  are 
usually  used  with  carbonate  of  soda  or  caustic  soda. 
The  following  is  a  much  used  formula: 

Phosphate  of  soda 6  Ibs. 

Bicarbonate  of  soda 6  Ibs. 

Water 40  gal. 

Both  of  these  substances  can  be  detected  by  the  well- 
known  qualitative  tests. 

43.  Combination  emulsifiers.     Frequently  a  combina- 
tion of  several  strong  emulsifiers  is  used.     The  follow- 
ing formula  has  had  an  extensive  use  by  several  large 
manufacturers : 

Chloride  of  lime 100  Ibs. 

Zinc  sulphate 25  Ibs. 

Lead  acetate      25  Ibs. 

Carbonate  of  soda 225  Ibs. 

Water 1200  gal. 

Wood  alcohol 30  gal. 

The  above  materials  are  dissolved  separately,  the 
solution  of  zinc  sulphate  and  of  lead  acetate  being 
added  to  the  chloride  of  lime  solution  (hot),  the  soda 
solution  added,  and  finally  the  alcohol,  which  is  added 


22  PAINT  AND  VARNISH  PRODUCTS. 

for  the  purpose  of  keeping  the  paint  in  storage  from 
freezing  in  winter.  The  above  solution  will  emulsify 
excellently  with  equal  quantities  of  linseed  oil.  The 
use  of  a  formula  of  this  type  cannot  be  beneficial  to 
the  paint. 


CHAPTER  IV. 

ESTIMATION  OF  LINSEED   OIL  AND  ITS  ADULTERATION  IN 
MIXED  PAINTS. 

44.  Separation  of  the  volatile  oils.  The  clear  oil  ob- 
tained by  settling  or  with  the  aid  of  the  centrifuge  is 
weighed  and  introduced  into  a  suitable-sized  Erlen- 
meyer  flask  connected  with  a  rather  large  condenser. 
The  contents  of  the  flask  are  brought  to  130°  C.  by 
means  of  an  oil  bath,  and  a  current  of  steam  as  dry  as 
possible  is  conducted  through  the  oil.  The  volatile  oils 
rapidly  distill  over  and  are  collected  in  a  weighed,  short- 
stemmed,  separatory  funnel,  the  water  being  drawn  off 
from  time  to  time  as  may  be  necessary.  Severe  froth- 
ing during  the  distillation  indicates  that  an  emulsify- 
ing agent,  such  as  caustic  soda  or  carbonate  of  soda,  has 
been  used.  The  frothing  can  be  overcome  by  the  addi- 
tion of  a  few  cubic  centimeters  of  dilute  sulphuric  acid 
to  neutralize  the  alkali  used.  The  distillate  is  allowed 
to  stand  for  several  hours  to  insure  the  complete  sepa- 
ration of  the  water,  which  is  then  drawn  off  and  the 
volatile  oils  weighed  and  bottled  for  subsequent  exam- 
ination. The  aqueous  portion  of  the  distillate  will  in- 
evitably carry  with  it  a  small  quantity  of  volatile  oil, 
but  the  quantity  will  be  slight,  amounting  to  about  0.4 
gram  per  100  c.c.  of  water  distillate.  After  obtaining 
the  percentage  of  volatile  oil  the  linseed  oil  is  calcu- 
lated by  difference,  by  subtracting  from  100  the  per- 
centages of  volatile  oil  and  water  present  in  the  paint. 

The  linseed  oil,  after  being  freed  from  the  volatile 
oils,  is  allowed  to  stand,  tightly  corked,  for  several  hours 

23 


24  PAINT  AND  VARNISH  PRODUCTS. 

in  a  warm  place  until  thoroughly  settled,  and  may  then 
be  tested  for  the  presence  of  other  oils. 

45.  Presence  of  driers.     The  linseed  oil  thus  obtained 
will  contain  the  Japan  or  drier  solids  present  in  the 
paint,  which  will  usually  be  of  a  rosin  nature.     In  the 
cheaper  class  of  paints,  and  especially  when  linseed 
oil  commands  a  high  price,  the  manufacturer  will  often 
obtain  relief  by  the  use  of  a  liberal  percentage  of  a 
cheap  benzine  drier  having  a  rosin  base. 

46.  Specific  gravity.     Determine  the  specific  gravity 
by  means  of  a  pycnometer  or  a  Westphal  balance. 

The  specific  gravity  may  be  taken  at  room  tempera- 
ture and  calculated  to  15.5°  C. 

Correction  for  1°  C.  =  .000650, 
Correction  for  1°  F.  =  .000361. 

The  accepted  limits  for  pure  raw  oil  at  15.5°  C.  are 
0.930  to  0.936  and  for  boiled  oils  0.937  to  0.945.  A 
low  specific  gravity  may  indicate: 

a.  Mineral  oils. 

b.  Cottonseed  oil. 

c.  Corn  oil. 

d.  Soya-bean  oil. 

A  high  specific  gravity  may  indicate: 

a.  Rosin  or  resinous  products. 
6.  Rosin  oils. 

c.  China  wood  oil. 

d.  Excessive  heating  or  unusual  addition  of  driers. 

47.  Spot  test.     One  or  2  c.c.  of  the  oil  are  poured  on 
a  porcelain  plate  and  a  drop  of  concentrated  sulphuric 
acid  is  added  carefully.     If  pure,  the  spot  formed  will 
bear  a  marked  resemblance  to  a  begonia  leaf.     If  rosin 


ESTIMATION  OF  LINSEED  OIL.  25 

or  rosin  oil  be  present  a  black,  gummy  mass  immediately 
results;  cottonseed  oil  gives  a  spot  without  the  char- 
acteristic markings  of  the  linseed-oil  spot.  Mineral 
oils  give  a  scum  band,  rapidly  spreading  out  over  the 
surface  from  the  drop,  the  margin  of  the  band  being 
uniformly  circular.  Fish  oils  give  a  similar  reaction, 
but  the  margin  of  the  band  is  not  at  all  uniform  and 
may  be  readily  distinguished  from  mineral  oils.  With 
a  little  practice  and  working  with  oils  of  known  com- 
position this  test  can  be  relied  upon  to  detect  any 
appreciable  adulteration  with  the  above  oils. 

48.  Mineral  oils.     The  spot  test  for  petroleum  prod- 
ucts may  be  confirmed  by  allowing  a  sample  of  the 
oil  to  flow  down  a  sheet  of  glass  the  other  side  of  which 
has  been  painted  jet  black.     If  petroleum  products 
are  present  even  in  a  minute  quantity,  the  sample  will 
exhibit  the  "bloom"  characteristic  of  mineral  oils.     A 
standard  sample  should  always  be  run  for  comparison. 
It  is  possible  to  remove  the  " bloom"  of  mineral  oils 
by  the  use  of  nitrobenzine,  nitronaphthalene,  or  similar 
compounds,  but  the  author  is  of  the  belief  that  this  is 
very  seldom  resorted  to  in  the  paint  industry. 

49.  Quantitative  estimation  of  mineral  oil.     Quantita- 
tively the  mineral  oil  may  be  estimated  by  saponifying 
10  grams  of  the  oil  with  alcoholic  potash  for  2  hours, 
using  a  return  condenser.     The  alcohol  is  distilled  off 
and  the  soap  dissolved  in  75  to   100  c.c.  of  water, 
transferred  to  a  separatory  funnel,  and  50  c.c.  of  ether 
added.     The  liquids   are  then  shaken,   avoiding  the 
formation   of   an   emulsion   as  far   as  possible.     The 
aqueous  solution  is  then  drawn  off,  the  ethereal  layer 
washed  with  a  few  cubic  centimeters  of  water  to  which 
a  little  caustic  potash  has  been  added,  and  poured  into 
a  weighed  flask.     The  soap  solution  is  then  returned 


26  PAINT  AND  VARNISH  PRODUCTS. 

to  the  separator,  and  twice  extracted  with  ether  in  the 
same  way  as  before. 

The  combined  ethereal  solutions  are  distilled  off  on 
the  water  bath,  the  flask  dried  and  weighed.  The  in- 
crease in  weight  represents  the  amount  of  unsaponi- 
fiable  matter,  and  unless  rosin  oil  is  present,  represents 
the  mineral  oil  with  the  exception  of  about  2  per  cent, 
the  average  amount  of  unsaponifiable  matter  in  lin- 
seed oil. 

50.  Separation  of  mineral  oil  from  rosin  oil.  The 
mineral  oil  may  be  separated  from  the  rosin  oil  in  the 
unsaponifiable  material  by  heating  50  c.c.  of  nitric 
acid  of  1.2  specific  gravity  to  boiling  in  a  flask  of 
700  c.c.  capacity,  the  source  of  heat  removed,  and  the 
unsaponifiable  material  added.  The  flask  is  then  heated 
on  the  water  bath  with  frequent  shaking  for  about  one- 
half  hour,  and  400  c.c.  of  cold  water  added.  After  cool- 
ing, 50  c.c.  of  petroleum  ether  is  added  and  the  flask 
agitated,  the  mineral  oil  is  dissolved,  while  the  resin- 
ous matters  remain  in  suspension.  The  liquid  is  then 
poured  into  a  separatory  funnel,  leaving  behind  as 
much  of  the  resinous  material  as  possible.  After  set- 
tling, the  aqueous  liquid  is  drawn  off  and  the  ethereal 
layer  poured  into  a  weighed  flask.  Another  portion 
of  petroleum  ether  is  added  to  the  rosin  remaining  in 
the  flask,  and  allowed  to  act  upon  it  for  about  ten 
minutes,  when  it  is  added  to  that  in  the  weighed  flask. 
After  distilling  off  the  ether  the  oil  is  weighed.  Min- 
eral oils  lose  about  10  per  cent  when  treated  with 
nitric  acid  in  this  way,  and  hence  the  weight  of  the 
oil  found  must  be  divided  by  0.9  in  order  to  find  the 
amount  present  in  the  sample  analyzed. 

5oa.  The  Outerbridge  test  for  mineral  oil  and  rosin  oil. 
A  few  drops  of  the  oil  to  be  tested  are  placed  between 


ESTIMATION  OF  LINSEED  OIL.  27 

two  plates  of  clear  glass,  placed  against  a  black  back- 
ground and  examined  by  reflected  light  from  an  enclosed 
arc  lamp,  adjusted  to  show  a  faint  rosy  light  in  addition 
to  the  powerful  white  light.  The  presence  of  mineral 
oil  is  evidenced  by  a  greenish  fluorescence,  and  rosin 
oil  by  a  bluish  fluorescence.  Even  the  so-called  de- 
bloomed  oils  show  up  strongly  under  this  test.  By 
preparing  a  set  of  standards  of  known  composition  as 
to  percentages  of  mineral  or  rosin  oils,  and  judging  the 
sample  under  examination  by  comparison,  reducing  it,  if 
necessary,  with  a  known  amount  of  pure  vegetable  oil 
until  it  corresponds  in  fluorescence  with  one  of  the 
standards,  the  approximate  percentage  of  rosin  or  min- 
eral oil  may  be  determined.  For  this  purpose  50  c.c. 
oil  test  bottles  may  be  used.  The  value  of  the  test 
depends  on  the  enormously  intensified  fluorescence  due 
to  the  particular  source  of  light  employed. 

51.  Cottonseed  oil.  This  oil  is  seldom  found  in 
house  paints,  but  is  often  used  in  the  cheaper  class  of 
barn  paints.  The  spot  test  may  be  confirmed  by  the 
Halphen  test,  the  apparatus  required  being  a  large 
test  tube  with  a  condensing  tube  and  a  brine  bath; 
the  reagent  employed  being  a  1.5  per  cent  solution  of 
sulphur  dissolved  in  carbon  bisulphide  with  an  equal 
volume  of  amyl  alcohol  added.  Equal  volumes  of  the 
oil  and  reagent  are  heated  in  a  steam  bath  at  first,  and, 
after  the  violent  boiling  has  ceased,  in  the  brine  bath 
at  105-110°  C.  for  about  30  minutes.  As  little  as  1 
per  cent  of  cottonseed  oil  will  give  a  crimson  wine 
coloration.  Cottonseed  oil  heated  to  250°  C.  does  not 
respond  to  this  test. 

Quantitatively,  the  amount  of  cottonseed  oil  can  only 
be  approximated  in  a  very  general  manner  by  means 
of  the  iodine  values. 


28  PAINT  AND  VARNISH  PRODUCTS. 

Let  x  =  percentage  of  one  oil  and 
y  =  percentage  of  the  other  oil, 
m  =  average  iodine  value  of  pure  oil  x, 
n  =  average  iodine  value  of  pure  oil  y,  and 
I  =  iodine  value  of  sample  under  examination, 

100  (7  -  n) 
then  x  = * L* 

m—n 

52.  Corn  oil.     This  oil  gives  a  spot  test  much  re- 
sembling that  given  by  linseed  oil,  but  may  be  detected 
in  linseed  oil,  if  in  quantity,  by  the  following  test: 
Dilute  with  four  volumes  of  benzine,  add  one  volume 
of  strong  nitric  acid,  shake.     Linseed  oil  turns  a  white 
color,  while  corn  oil  turns  a  reddish  orange. 

Quantitatively  corn  oil  can  be  estimated  only  ap- 
proximately when  in  linseed  oil,  by  the  same  method 
used  for  cottonseed  oil. 

53.  Fish  oils.     In  addition  to  the  spot  test  these  oils 
may  be  detected  by  rubbing  a  little  of  the  sample 
vigorously  between  the  palms  of  the  hands.     Fish-oil 
mixtures  give  the  characteristic  odor  of  oils  of  this 
class. 

54.  In  case  of  doubt  the  Eisenschyml  test l  may  be 
used:   One  hundred  drops  of  the  oil  are  dissolved  in 
6  c.c.  of  a  mixture  containing  equal  parts  of  chloroform 
and  glacial  acetic  acid.     Bromine  is  added   drop  by 
drop  until  the  brown  coloration  remains.     After  10  to 
15  minutes  the  test  tube  is  placed  in  a  beaker  contain- 
ing boiling  water.    Linseed  oil  and  other  vegetable  oils, 
such  as  China  wood  oil,  cottonseed  oil,  corn  oil,  etc., 
will  clear  up  completely  within  a  few  seconds,  while 
fish  oils  will  remain  cloudy  and  precipitate  an  insolu- 
ble bromide  at  the  bottom  of  the  tube  after  a  short 

1  J.  Ind.  and  Eng.  Chemistry,  Feb.,  1910. 


ESTIMATION  OF  LINSEED  OIL.  29 

time.  With  a  little  practice  5  per  cent  of  fish  oil  is 
clearly  recognizable. 

In  the  case  of  boiled  linseed  oil  it  is  necessary  to 
remove  the  metallic  constituents  before  adding  the  bro- 
mine. This  is  preferably  done  by  shaking  with  a  10 
per  cent  solution  of  nitric  acid  saturated  with  potas- 
sium nitrate. 

In  mixtures  with  linseed  oil  the  amount  present  can 
only  be  determined  crudely,  by  means  of  the  "rise  of 
temperature"  with  sulphuric  acid  with  the  Maumene 
apparatus  described  under  the  analysis  of  the  volatile 
oils  (Allen  found  the  rise  of  temperature  with  sul- 
phuric acid  to  be  104  to  111  in  the  case  of  linseed  oil, 
and  126  in  the  case  of  menhaden  oil),  or  else  by  weigh- 
ing the  insoluble  bromides  according  to  the  procedure 
described  by  Eisenschyml.  Fish  oils  are  used  only  "to 
a  limited  extent  in  paints. 

55.  Rosin  and  rosin  oils.  These  products  are  best 
detected  qualitatively  by  means  of  the  Liebermann- 
Storch  reaction,  which  is  of  sufficient  delicacy  to  de- 
tect the  presence  of  even  very  small  quantities  of  rosin 
oil  or  rosin  drier  in  boiled  oil.  Shake  1  to  2  c.c.  of  the 
oil  under  examination  in  a  test  tube  with  acetic  anhy- 
drides at  a  gentle  heat,  cool,  pipette  off  the  anhydride, 
and  place  a  few  drops  on  a  porcelain  crucible;  cover, 
and  add  one  drop  of  sulphuric  acid  (34.7  c.c.  sulphuric 
acid  and  35.7  c.c.  water)  so  that  it  will  mix  slowly. 
If  rosin  or  rosin  oil  is  present  a  characteristic  violet, 
fugitive  color  results.  Certain  fish  oils  will  give  a  very 
similar  color,  but  if  present  are  easily  detected  by  the 
fishlike  odor  of  the  oil  on  warming. 

Old  samples  of  pure  boiled  oil  give  a  color  that 
might  be  easily  mistaken  for  rosin  or  rosin  oils;  in  such 
cases  it  is  best  to  warm  the  oil  with  alcohol  so  as  to 


30  PAINT  AND  VARNISH  PRODUCTS. 

extract  the  bulk  of  rosin  present  and  test  the  alcoholic 
extract.  Rosin  may  be  more  completely  separated  and 
estimated  by  Twitchell's  process  (J.  Soc.  Chem.  Ind., 
1891,  10,  804)  or  by  Cladding's  method  (Amer.  Chem. 
J.,  3,  416).  This  process  depends  upon  the  solubility 
of  silver  resinate  in  ether,  while  the  silver  salts  of  fatty 
acids  are  insoluble. 

56  Soya-bean  oil.  This  oil  has  come  into  use  quite 
largely  during  the  last  two  years.  Its  chemical  and 
physical  properties  are  so  nearly  like  those  of  linseed 
oil  that  it  is  difficult  to  detect  it  with  certainty  when 
mixed  with  linseed  oil.  In  such  mixtures  "the  spot  test 
exhibits  a  yellowish-green  fluorescent  color  which  is 
clearly  recognized,  but  in  the  presence  of  a  rosin  drier 
this  reaction  is  masked.  When  used  to  adulterate  lin- 
seed oil  an  excessive  amount  of  drier  is  usually  added 
in  order  to  overcome  the  slow  drying  of  the  soya-bean 
oil.  Unlike  linseed  oil  it  does  not  bleach  when  strongly 
heated,  but  becomes  several  shades  darker. 

57.  Constants  of  soya-bean  oil. 

Specific  gravity 0.923-0.924 

Acid  number 190 

Saponification  number 188-188.5 

Iodine  number 127-136 

Average  iodine  number 131 

Often  as  much  as  25  per  cent  of  soya-bean  oil  may 
be  added  to  linseed  oil  before  the  iodine  number  will 
be  lowered  sufficiently  strongly  to  indicate  such  adul- 
teration. However,  if  the  iodine  number  is  below  170 
(Hubl)  the  presence  of  soya-bean  oil  may  be  strongly 
suspected.  The  oxygen  absorption  test  will  also  yield 
information  of  value. 

58.  In  the  preparation  of  gloss  paints  a  little  varnish 
is  added,  the  gums  of  which  might  be  mistaken  in  the 


ESTIMATION   OF  LINSEED  OIL.  31 

above  tests  for  rosin.  In  the  cheaper  paints  a  large 
excess  of  rosin  is  used  in  the  resinate  drier  added.  An 
easy  method  of  detecting  rosin  and  other  resins  and 
estimating  the  relative  amount  present  is  to  stir  up 
about  100  grams  of  the  paint  with  500  c.c.  petroleum 
ether,  allow  to  stand  24  hours  in  a  cold  place,  siphon 
off  the  ether,  and  examine  the  skin  formed  on  top  of 
the  pigment.  This  will  harden  in  the  course  of  an- 
other day  so  that  it  may  be  removed,  placed  on  a 
watch  glass,  washed  free  of  adhering  pigment  with 
more  petroleum  ether,  and  dried.  The  color  and  other 
physical  properties  will  enable  one  to  judge  whether  it 
is  rosin  or  some  of  the  other  varnish  gums. 

59.  China  wood  oil.  The  constants  of  China  wood  oil 
run  quite  uniform.  The  Hanus  iodine  method  gives 
an  iodine  number  abnormally  high.  The  Hubl  modifi- 
cation yields  the  best  results,  a  6-hour  absorption  being 
sufficient. 

Specific  gravity 0.941-0.943 

Free  acid  value 4-4 . 5 

Saponification  number 190.8-191 

Hubl  iodine  number  163-175 


CHAPTER  V. 

DETERMINATION  OF  THE  PURITY  OF  LINSEED   OIL. 

60.  The  paint  chemist  is  frequently  required  to  pass 
on  the  purity  and  quality  of  linseed  oil,  both  raw  and 
boiled,  and  must  therefore  determine  its  analytical  char- 
acteristics with  much  care.     The  following  example  rel- 
ative to  a  pure  raw  linseed  oil  is  illustrative  of  the  data 
usually  required: 

Specific  gravity  at  60°  F.  (15.5°  C.) 0.9334 

Iodine  value 174 . 

Unsaponifiable  matter 1.1  per  cent 

Saponifiable  value 191.8 

Acid  value 2.8 

Rosin  test Negative 

Time  of  drying,  50  hours  as  against  52  hours 
with  standard  sample 

Loss  at  100°  C 0.10  per  cent 

Color,  odor,  and  taste  similar  to  standard. 

The  above  determination  can  often  be  supplemented 
with  advantage  by  .data  derived  from  the  following 
estimations : 

Flash  test.  Oxygen  absorption. 

Maumene"  figure.  Bromination  figure. 

Refractive  index  at  15°  C.  Hexabromide  test. 

61.  Specific  gravity.     The  specific  gravity  of  a  raw  lin- 
seed oil  should  lie  between  0.930  and  0.936,  and  that  of 
boiled  linseed  oil  between  0.937  and  0.945.     All  adulter- 
ants except  rosin  and  rosin  oil  would  lower  the  specific 
gravity. 

62.  Determination  of  the  iodine  number.     The  newer 
Hanus  method  for  the  estimation  of  the  iodine  number 

32 


THE  PURITY  OF  LINSEED  OIL.  33 

is  to  be  preferred  to  the  older  standard  Hiibl  method, 
as  the  Hubl  solution  rapidly  loses  strength  on  standing 
and  is  very  slow  in  its  reaction.  Nearly  every  chemist 
using  it  employs  a  modification  of  his  own,  especially  as 
regards  the  time  for  the  solution  to  remain  in  contact 
with  the  fat  or  oil,  and  hence  very  different  results  may 
be  obtained  on  the  same  oil  or  fat  by  different  investi- 
gators. Comparative  tests  by  the  two  methods  made 
in  this  laboratory  gave  results  which  varied  only  a  few 
tenths  of  one  unit. 

63.  Preparation  of  reagents.  Iodine  solution.  Dis- 
solve 13.2  grams  of  iodine  in  1000  c.c.  glacial  acetic  acid 
(99.5  per  cent  acid,  showing  no  reduction  with  bichro- 
mate and  sulphuric  acid) ;  add  enough  bromine  to  double 
the  halogen  content  determined  by  titration  —  3  c.c.  of 
bromine  is  about  the  proper  amount.  The  iodine  may 
be  dissolved  by  the  aid  of  heat,  but  the  solution  should 
be  cold  when  bromine  is  added. 

Decinormal  sodium  thiosulphate  solution.  Dissolve 
24.8  grams  of  chemically  pure  sodium  thiosulphate, 
freshly  pulverized,  as  finely  as  possible  and  dried  between 
filter  or  blotting  paper,  and  dilute  with  water  to  one 
liter  at  the  temperature  at  which  the  titrations  are  to 
be  made. 

Starch  paste.  One  gram  of  starch  is  boiled  in  200  c.c. 
of  distilled  water  for  ten  minutes  and  cooled  to  room 
temperature. 

Solution  of  potassium  iodide.  One  hundred  and  fifty 
grams  of  potassium  iodide  are  dissolved  in  water  and 
made  up  to  one  liter. 

Decinormal  potassium  bichromate.  Dissolve  4.9066 
grams  of  chemically  pure  potassium  bichromate  in  dis- 
tilled water  and  make  the  volume  up  to  one  liter  at 
the  temperature  at  which  the  titrations  are  to  be  made. 


34  PAINT  AND  VARNISH  PRODUCTS. 

The  bichromate  solution  should  be  checked  against 
pure  iron. 

64.  Determination.    Standardizing  the  sodium  thiosul- 
phate  solution.     Place  20  c.c.  of  the  potassium  bichrom- 
ate solution,  to  which  has  been  added  10  c.c.  of  the 
solution  of  potassium  iodide,  in  a  glass-stoppered  flask. 
Add  to  this  5  c.c.  of  strong  hydrochloric  acid.     Allow 
the  solution  of  sodium  thiosulphate  to  flow  slowly  into 
the  flask  until  the  yellow  color  has  almost  disappeared. 
Add  a  few  drops  to  the  starch  paste,  and  with  constant 
shaking  continue  to  add  the  sodium  thiosulphate  until 
the  blue  color  just  disappears. 

65.  Weighing  the  sample.    Weigh  about  0.5  gram  of 
fat  or  0.250  gram  of  oil  on  a  small  watch  glass  or  by 
other  suitable  means.     With  drying  oils  which  have  a 
very  high  absorbent  power  0.100  to  0.200  gram  should 
be  taken.     The  fat  is  first  melted,  mixed  thoroughly, 
poured  onto  the  crystal,  and  allowed  to  cool.     Intro- 
duce the  watch  crystal  into  a  wide-mouthed  16-ounce 
bottle  with  a  ground-glass  stopper. 

66.  Absorption  of  iodine.     The  fat  or  oil  in  the  bottle  is 
dissolved  in  10  c.c.  of  chloroform.     After  complete  solu- 
tion has  taken  place,  25  c.c.  of  the  iodine  solution  are 
added.     Allow  to  stand  with  occasional  shaking  for 
30  minutes.     The  excess  of  iodine  should  be  at  least 
60  per  cent  of  the  amount  added. 

67.  Titration  of  the  unabsorbed  iodine.    Add  10  c,c.  of 
the  potassium  iodide  solution  and  shake  thoroughly, 
then  add  100  c.c.  of  distilled  water  to  the  contents  of  the 
bottle.     Titrate  the  excess  of  iodine  with  the  sodium 
thiosulphate  solution,  which  is  added  gradually,  with 
constant  shaking,  until  the  yellow  color  of  the  solution 
has  almost  disappeared.     Add  a  few  drops  of  starch 
paste  and  continue  the  titration  until  the  blue  color 


THE  PURITY  OF  LINSEED  OIL  35 

i 

has  entirely  disappeared.  Toward  the  end  of  the  reac- 
tion stopper  the  bottle  and  shake  violently,  so  that  any 
iodine  remaining  in  solution  in  the  chloroform  may  be 
taken  up  by  the  potassium  iodide  solution. 

68.  Setting  the  value  of  the  iodine  solution.     At  the  time 
of  adding  the  iodine  solution  to  the  fat  two  bottles  of 
the  same  size  as  those  used  for  the  determination  should 
be  employed  for  conducting  the  operation  described 
above,  but  without  the  presence  of  any  fat.     In  every 
other  respect  the  performance  of  the  blank  experiments 
should  be  just  as  described.     These  blank  experiments 
should  be  made  each  time  the  iodine  solution  is  used. 
Great  care  must  be  taken  that  the  temperature  of  the 
solution  does  not  change  during  the  time  of  the  opera- 
tion, as  acetic  acid  has  a  very  high  coefficient  of  ex- 
pansion, and  a  slight  change  of  temperature  makes  an 
appreciable  difference  in  the  strength  of  the  solution. 

69.  A  freshly  prepared  linseed*  oil  will  have  an  iodine 
value  of  about  185  to  187;  this  will  rapidly  drop  to 
about  180,  and  when  suitably  aged  will  have  decreased 
to  about  175,  although  an  old  oil  may  have  an  iodine 
value  as  low  as  170.     This  figure,  however,  should  be 
regarded  as  the  lowest  acceptable  limit.     Boiled  linseed 
oil  as  prepared  for  paint  purposes  will  show  an  iodine 
number  ranging  between  160  and  175.     Specially  boiled 
oils  may  have  an  iodine  number  as  low  as  150. 

70.     IODINE  NUMBERS  OF  VARIOUS  OILS. 

China  wood  oil 163-175 

Cora  oil 111-125 

Cottonseed  oil 101-117 

Fish  oil 148-180 

Rosin  oils 40-  65 

Petroleum  products 4-20 

Soya-bean  oil       127-136 

Turpentine 320-385 


36  PAINT  AND  VARNISH  PRODUCTS. 

A 

71.  Unsaponifiable  matter.     The  method  for  determin- 
ing the  unsaponifiable  matter  has  been  stated  in  the  pre- 
ceding chapter.     A  raw  linseed  oil  should  not  contain 
more  than  1.6  per  cent  of  unsaponifiable  matter  and 
may  contain  as  little  as  0.5  per  cent.     A  boiled  oil  will 
usually  contain  a  slightly  higher  percentage,  varying 
between  the  limits  of  1  and  2  per  cent. 

The  unsaponifiable  matter  in  linseed  oil  consists  essen- 
tially of  waxes  and  complex  alcohols. 

72.  Determination   of   the    saponification   value.     This 
value  is  also  spoken  of  as  the  Koettstorfer  number  and 
the  saponification  number.     In  each  case  it  is  equiva- 
lent to  the  number  of  milligrams  of  potassium  hydroxide 
necessary  to  saponify  one  gram  of  the  oil. 

Two  grams  of  the  oil  are  weighed  out  into  a  small 
Erlenmeyer  flask  and  saponified  with  25  c.c.  of  half- 
normal  alcoholic  potash,  by  heating  gently  on  a  water 
bath,  a  funnel  being  inserted  in  the  flask.  When  the 
saponification  is  complete  a  few  drops  of  phenolphtha- 
lein  are  added  and  the  excess  of  alkali  titrated  with  half- 
normal  hydrochloric  acid.  A  blank  determination  of 
the  strength  of  the  alcoholic  potash  should  be  made  at 
the  same  time. 

The  saponification  value  of  raw  linseed  oil  should  lie 
above  189  and  of  boiled  linseed  oil  above  197. 

73.  Determination  of  the  free  fatty  acids  in  linseed  oil. 
Ten  grams  of  oil  are  weighed  into  a  suitable-sized  Erlen- 
meyer flask  and  50  c.c.  of  neutral,  aldehyde-free  alcohol 
added.     The  mixture  is  heated  to  about  60°  C.  for  a 
minute  or  two,  then  cooled  and  titrated  with  tenth 
normal  alcoholic  potash,  using  phenolphthalein  as  an 
indicator. 

Oil  made  from  moldy  seed,  or  seed  contaminated 
with  mustard  oil,  or  oil  containing  rosin,  will  have  a 


THE  PURITY  OF  LINSEED  OIL.  37 

high  acid  figure.     Pure  raw  oil  should  have  a  low  acid 
figure;  boiled  oil  will  have  a  slightly  higher  figure. 

74.  Preparation  of  aldehyde-free  alcohol  for  alcoholic 
potash  solution.     Dissolve  1.5  grams  of  silver  nitrate  in 
about  3  c.c.  of  water  and  add  to  a  liter  of  alcohol  in  a 
glass-stoppered  cylinder,  mixing  thoroughly.     Dissolve 
3  grams  of  pure  potassium  hydroxide  in  10  to  15  c.c.  of 
warm  alcohol.     Cool,  pour  slowly  into  the  alcoholic 
silver  nitrate  solution,   without  shaking.     The  silver 
oxide  is  precipitated  in   a  finely  divided   condition. 
Allow  to  stand  until  the  precipitate  has  completely 
settled.     Siphon  off  the  clear  liquid  and  distill.     The 
distillate  will  be  neutral  and  free  from  aldehydes,  and 
will  not  darken  when  used  as  a  solvent  for  potash. 

The  acid  value  of  raw  linseed  oil  is  between  1  and  5 
and  of  boiled  linseed  oil  between  4  and  12,  averaging 
between  7  and  8.  Rosin  and  rosin  in  oils,  if  present, 
would  materially  raise  the  acid  value,  as  rosin  has  an  acid 
value  of  from  120  to  150  and  rosin  oil  from  20  to  50. 

75.  Free   mineral   acid.    Any   free    mineral    acid    in 
bleached  oil  is  determined  by  washing  a  definite  weight 
of  oil  with  water,  separating  the  water,  and  titrating  the 
dissolved  mineral  acid  present.     Any  mineral  acid  found 
will  usually  be  sulphuric  acid.     Its  presence  is  decidedly 
objectionable. 

Varnish  oil.  A  specially  refined  linseed  oil  is  used 
in  the  manufacture  of  varnishes,  and  it  often  devolves 
upon  the  paint  chemist  to  pass  on  such  oils.  It  is  not 
safe  to  judge  the  color  of  the  oil  from  the  sample  as 
received,  but  it  should  be  heated  in  a  beaker  slowly,  to 
the  temperature  required  in  the  varnish  kettle,  and 
after  cooling  the  color  should  be  compared  with  the 
standard  sample,  which  should  be  kept  in  a  dark 
place.  Some  varnish  oils  will  bleach  considerably 


38  PAINT  AND  VARNISH  PRODUCTS. 

under  heat,  and  others  slightly  or  not  at  all.  Varnish 
oils  act  on  the  varnish  gums  very  differently  in  the 
varnish  kettle;  some  flux  with  the  gum  easily;  others 
combine  with  the  gum  with  difficulty,  requiring  an  ex- 
cess of  heat  and  a  longer  time  to  cook,  often  affording  a 
varnish  of  quite  dissimilar  properties.  It  is  therefore 
advisable  for  the  chemist  to  have  the  varnish  oil  under 
examination  thoroughly  tried  out  in  the  varnish  kettle 
before  approving  it. 

76.  Determination  of  the  flash  point  of  linseed  oil.  For 
exact  flash-point  figures  rather  expensive  and  compli- 
cated testers  are  needed,  but  for  commercial  tests  that 
yield  approximately  the  same  figures  a  very  simple 
apparatus  may  be  used,  consisting  of  a  two-ounce  cru- 
cible, a  thermometer  reading  at  least  300°  C.,  and  a 
small  gas  jet  attached  to  a  rubber  tube,  a  flame  about 
the  size  of  a  pea  being  used.  The  cup  is  filled  two- 
thirds  full  of  oil,  the  bulb  of  the  thermometer  suspended 
in  it,  and  the  oil  slowly  heated.  The  determination 
should  be  carried  on  in  a  place  entirely  free  from  drafts. 
At  short  intervals  the  gas  flame  is  brought  close, 
but  without  touching,  to  the  surface  of  the  oil,  with  a 
slow,  sweeping  motion.  The  first  distinct  puff  of  pale- 
blue  flame  that  shoots  across  the  surface  of  the  oil  in- 
dicates the  flash  point  of  the  oil,  and  the  temperature 
at  which  this  occurs  is  noted. 

Hurst  states  that  linseed  oil,  whether  raw  or  boiled, 
flashes  at  about  243°  C.,  but  these  figures  are  consider- 
ably lower  than  those  obtained  in  this  laboratory,  the 
raw  oils  flashing  in  the  vicinity  of  300°  C.  and  the  pure 
boiled  oils  from  275°  to  300°  C.  Volatile  oils  used  in 
the  drier  added  to  the  oil  lower  the  flash  point  consider- 
ably, 4  or  5  per  cent  of  volatile  oil  lowering  the  flash 
point  to  about  250°  C.  The  other  vegetable  oils,  as 


THE  PURITY  OF  LINSEED  OIL.  39 

corn  and  cottonseed  oils,  flash  at  nearly  the  same  tem- 
perature as  linseed  oil.  Mineral  oils,  such  as  would 
be  used  for  adulteration,  flash  at  193°  to  216°  C., 
rosin  oils  at  140°  to  167°  C.  The  presence  of  rosin  oil 
would  also  be  indicated  by  the  strong  odor  of  rosin 
given  off  during  the  heating.  Benzine  and  turpentine 
when  present  in  linseed  oil  rapidly  lower  the  flash  point 
according  to  the  percentage  present,  having  a  flash 
point  themselves  but  little  above  that  of  room  tem- 
perature. 

77.  Correction  to  be  applied  to  the  thermometer  reading. 
Let       N  =  Length  of  exposed  thread  of  mercury  ex- 
pressed in  degrees. 

T  =  observed  boiling  point. 
i  =  temperature  of  the  auxiliary  thermometer, 
the  bulb  of  which  is  midway  between 
the  ends  of  the  exposed  mercury  thread. 
0.000154  =  apparent  coefficient  of  expansion  of  mer- 
cury in  glass. 

C  =  the  correction  in  degrees. 
Then    C  =  N(T  -  i)  X  0.000154. 

78.  Linseed  oil  from  inferior  seed.     This  includes  oil 
prepared  from  impure  or  adulterated  seed,  giving  an 
oil  of  inferior  quality,  or,  what  is  essentially  the  same 
thing,  the  screened  foreign  seeds  are  separately  crushed 
and  pressed  and  the  resulting  oil  used  to  blend  with  a 
pure  linseed  oil.     Such  oils  dry  slowly  and  imperfectly, 
and  the  resulting  film  lacks  the  " hardness"  given  by 
the  pure  oils,  and  often  give  the  consumer  as  just  cause 
for  complaint  as  the  more  grossly  adulterated  varieties. 

79.  When  sold  as  raw  oil,  such  oils  usually  have  a" 
greenish  tinge,  which  disappears  or  is  masked  in  the 
boiling.     Chemically  this  form  of  adulteration  is  more 
difficult  to  detect  than  when  other  oils  of  distinctly 


40  PAINT  AND  VARNISH  PRODUCTS. 

different  chemical  properties  are  used.  With  this  class 
of  oils  the  specific  gravity,  iodine  number,  saponifica- 
tion  value,  and  unsaponifiable  matter  remain  nearly 
normal,  and  the  leading  tests  that  may  be  applied  to 
such  suspected  oils  are  their  oxygen  absorption  power 
and  the  time  required  for  drying.  Both  the  per  cent 
of  oxygen  and  the  rate  of  absorption  will  be  found 
markedly  lower,  depending  on  the  amount  of  foreign 
seed  oil  present.  In  order  to  obtain  comparable  re- 
sults, a  standard  oil  of  known  purity  should  be  carried 
through  the  tests  along  with  the  suspected  oil,  as  the 
weather  conditions  may  seriously  affect  the  rate  of 
drying. 

80.  Spread   about   one   gram   of  precipitated    lead, 
weighed  off  accurately,   on  a  somewhat  large  watch 
glass  in  a  thin  layer,  and  then  allow  to  fall  onto  it  from 
a  pipette  0.6  to  0.7  gram  (not  more)  of  the  oil  to  be 
tested,  placing  each  drop  on  a  different  portion  of  the 
lead  and  taking  care  that  the  drops  do  not  run  into  one 
another.     Then  allow  the  watch  glass  to  stand  at  the 
ordinary  temperature  in  a  place  exposed  to  light  and 
protected  from  falling  dust.     Weigh  at  frequent  inter- 
vals in  order  to  note  the  rapidity  with  which  the  oil 
is  absorbing  oxygen  and  to  determine  accurately  when 
the  oil  ceases  to  gain  weight.     The  lead  powder  is  pre- 
pared by  precipitating  a  lead  salt  with  zinc,  washing 
the  precipitate  rapidly  in  succession  with  water,  alco- 
hol, and  ether,  and  finally  drying  in  a  vacuum. 

81.  Instead    of    precipitated    lead,    thin    aluminum 
plates  3  inches  by  6  inches  may  be  used.     The  plates 
are  weighed  and  0.1  gram  or  0.2  gram  of  oil  rubbed 
over  the  plate,  giving  a  thin,  uniform  film,  weighed,  set 
aside  in  a  dust-free  place,  and  the  increase  in  weight 
noted  from  time  to  time. 


THE  PURITY  OF  LINSEED  OIL.  41 

The  oxygen  absorption  figure  of  a  freshly  prepared 
linseed  oil  is  usually  between  18  and  19  per  cent.  This 
percentage  will  diminish  somewhat  during  the  aging 
process,  but  should  not  go  below  16.  On  the  other 
hand,  a  boiled  oil  may  have  an  oxygen  absorption  as 
low  as  14  per  cent  but  will  average  about  16  per  cent. 
The  oxygen  absorption  of  oils  added  as  adulterants 
and  weed  seed  oils  which  may  be  present  decrease  the 
oxygen  absorption  value. 

82.  Composition  of  linseed  oil  foots.1  The  foots  from 
linseed  oil,  manufactured  by  the  naphtha  extraction 
process,  after  centrifuging,  contained  75.8  per  cent  lin- 
seed oil,  the  extraction  being  conducted  with  carbon 
disulphide.  The  insoluble  portion  contained: 

Per  cent. 

SiO2 34.38 

CaO  .    .    .:.,-.;  .   ; 7.98 

MgO 8.39 

P2O5 46.50 

K2O Present 

97.17 

The  foots  from  an  hydraulic  pressed  linseed  oil 
contained : 

Per  cent. 

SiO2 None 

CaO 3.26 

MgO 4.99 

K2O 10.27 

P2O6 81.08 

99.08 

1  Eisenschyml,  J.  Ind.  and  Eng.  Chem.,  Jan.,  1910, 


CHAPTER  VI. 

DETERMINATION  OF  THE  PURITY  OF  LINSEED  OIL 

(Continued). 

83.  Determination  of  the  bromine  absorption  figure, 
Mcllhiney's  method.1  The  advantage  of  this  method 
is  that  the  absorption  of  halogen  by  addition  is  deter- 
mined separately  from  the  absorption  by  substitution, 
resulting  in  additional  information  as  to  the  nature  of 
the  substance. 

The  process  as  at  present  used  is  as  follows:  A  quan- 
tity of  the  oil  to  be  analyzed  is  weighed  into  a  glass- 
stoppered  bottle,  10  c.c.  of  carbon  tetrachloride  added 
to  dissolve  the  oil,  and  20  c.c.  of  third-normal  bromine 
in  carbon  tetrachloride  added  from  a  pipette.  It  is 
not  found  necessary  in  filling  the  pipette  with  bromine 
solution  to  use  any  special  arrangement  to  prevent  the 
introduction  of  bromine  vapor  into  the  mouth.  Only  a 
rubber  tube  is  necessary.  Another  pipette  full  of  solu- 
tion should  be  added  to  10  c.c.  of  carbon  tetrachloride^ 
and  this  blank  titrated  with  thiosulphate  to  determine 
the  strength  of  the  bromine  solution.  The  test  itself 
need  be  allowed  to  stand  only  one  or  two  minutes 
before  adding  20  to  30  c.c.  of  10  per  cent  solution  of 
potassium  iodide,  the  .amount  necessary  depending  upon 
the  excess  of  bromine  present.  An  excess,  of  course, 
does  no  harm.  In  order  to  prevent  any  loss  of  bromine 
or  hydrobromic  acid  which  would  probably  occur  on 
removing  the  stopper  of  the  bottle,  a  short  piece  of 
wide  rubber  tubing,  of  the  sort  used  for  Gooch  cru- 

1  J.  Am.  Chem.  Soc.,  XXI,  1084. 
42 


THE  PURITY  OF  LINSEED  OIL.  43 

cibles,  is  slipped  over  the  lip  of  the  bottle  so  as  to  form 
a  well  around  the  stopper.  It  is  advisable,  also,  to 
cool  the  bottle  by  setting  it  into  cracked  ice  in  order  to 
produce  a  partial  vacuum  in  the  interior.  Into  the  well 
formed  by  the  rubber  tubing  is  poured  the  solution  of 
potassium  iodide  and  the  stopper  opened  slightly.  If 
the  bottle  has  been  cooled  with  ice  the  iodide  solution 
will  be  sucked  into  the  bottle,  and  if  it  was  not  cooled 
some  of  the  air  from  the  interior  of  the  bottle  will 
bubble  through  the  iodide  solution,  being  thereby 
washed,  and  allow  the  iodide  solution  to  enter  the 
bottle.  When  sufficient  iodide  solution  has  been  in- 
troduced the  bottle  is  agitated  to  insure  the  absorption 
of  the  bromine  and  hydrobromic  acid  by  the  aqueous 
solution.  The  iodine  now  present  is  titrated  with  tenth- 
normal  sodium  thiosulphate,  and  when  the  titration  is 
finished  5  c.c.  of  a  neutral  2  per  cent  solution  of  potas- 
sium iodate  is  added.  This  liberates  a  quantity  of 
iodine  equivalent  to  the  hydrobromic  acid  formed,  and 
on  titrating  this  iodine  the  bromine  substitution  figure 
may  be  calculated.  The  solution  of  potassium  iodate 
should  be  tested  for  acidity  by  adding  a  measured 
quantity  to  a  solution  of  potassium  iodide,  and  if  any 
iodine  is  liberated  it  should  be  determined  jvith  thio- 
sulphate and  a  suitable  correction  introduced  into  the 
calculation.  The  potassium  iodide,  the  thiosulphate 
solution,  and  the  water  used  should  all  be  tested  to  see 
that  they  are  neutral. 

The  action  between  bromine  and  oil  appears  to  be 
practically  instantaneous  as  far  as  the  bromine  taken 
up  by  addition  is  concerned,  but  it  seems  likely  that 
substitution  is  distinctly  affected  by  the  length  of  time 
that  the  oil  and  bromine  are  allowed  to  remain  in 
contact. 


44 


PAINT  AND  VARNISH  PRODUCTS. 


84.  BROMINE  VALUES  OF  VARIOUS  OILS. 


1 

E 

3 

:3 

m 

Bromine  Calculated 
from  Hubl. 

Per  Cent  of  Bromine  Ab- 
sorbed. 

Bromine  Addition 
Figure. 

Bromine  Substitution 
Figure. 

Bromine  from  Hubl  Di- 
vided by  Bromine  Ad- 
dition Figures. 

Raw  linseed  oil,  several 
years  old 

1 

166  9 

105.2 

98.4 

95   4 

1  5 

1  103 

Raw  linseed  oil,  several 
years  old     
Raw  linseed  oil      ... 
Do 

2 
3 
4 

157.3 

184.2 
178  6 

99.1 
116.1 
112.6 

99.2 
116.1 
108.5 

92.0 

109.6 
102.1 

3.6 
3.4 
3  2 

1.000 
1.059 
1  102 

Do                ... 

5 

185  9 

117.2 

113.2 

109  2 

2  0 

1  072 

Do. 

6 

186.3 

117.0 

112.2 

106.5 

2  9 

1  098 

Do. 

7 

104.5 

99.9 

2  3 

Do  

8 

115.1 

109.5 

2  8 

Do  

q 

114.6 

109.4 

2  6 

Average,  omitting  Nos. 
1  and  2 

183  8 

115  7 

112  0 

106  6 

2  7 

1  083 

Boiled  linseed  oil  .   .   . 
Do  
Do. 

1 
2 

3 

180.4 
183.3 

113.7 
115.5 

106.0 
110.8 
105  4 

100.8 
105.8 
101  2 

2.6 
2.5 
2  1 

1.126 
1.091 

Do. 

4 

110  0 

103  2 

3  4 

Do.    . 

5 

109  8 

105  2 

2  3 

Do. 

6 

113  6 

103  0 

5  3 

Do.    . 

7 

109  2 

103  8 

2  7 

Do.    .              ... 

g 

110  8 

101  0 

4  9 

Averages     ... 

109.5 

103  0 

3  2 

Third-run  rosin  oil   .   . 
Do. 

1 

9 

63  9 

40  3 

197.6 
92  3 

16.4 

7  7 

90.6 
42  3 

5  231 

"Mystic"  brand  rosin 
oil  .    . 

93  7 

6  3 

43  7 

"  Java  "  boiled  rosin  oil 
Corn  oil   

1 

73.3 

46.2 

101.9 
76  2 

8.3 
73  8 

46.8 
1  2 

5.685 

Do.    . 

? 

75.8 

73.2 

1.3 

Do. 

3 

75  4 

71  6 

1  9 

Averages     

75.8 

72.9 

1.5 

THE  PURITY  OF  LINSEED  OIL.  45 

85.  Estimation  of  rosin  in  mixtures  of  linseed  oil  and 
mineral    oil.    Twitchell's   method.    A   weighed    portion 
of  the  sample  is  saponified  by  boiling  with  alcoholic 
potash,  and  the  alcohol  is  driven  off  by  prolonged  boiling 
after  diluting  with  water.     The  unsaponifiable  matter 
is  shaken  out  with  petroleum  ether,  as  previously  de- 
scribed under  linseed  oil,  the  remaining  soap  solution 
made  acid  yielding  a  mixture  of  fatty  and  rosin  acids. 
Heat  until  the  fatty  acids  have  separated  on  top.     Cool, 
break  the  cake  of  fatty  acids  with  a  glass  rod,  pouring 
off  the  aqueous  solution.     Treat  the  acids  again  with 
boiling  water,  cool,  remove  to  a  porcelain  dish,  and  dry 
at  100°  C.  until  freed  from  all  traces  of  water. 

Two  to  three  grams  of  the  mixed  fatty  and  rosin  acids 
are  weighed  off  accurately  and  dissolved  in  a  flask  in  ten 
times  their  volume  of  absolute  alcohol,  and  a  current  of 
dry  hydrochloric  acid  gas  is  passed  through  for  about 
forty-five  minutes  or  until  the  gas  ceases  to  be  ab- 
sorbed. Allow  to  stand  one  hour,  then  dilute  it  with 
five  times  its  volume  of  water  and  boil  until  clear. 
From  this  point  the  analysis  may  be  completed  volu- 
metrically  or  gravimetrically. 

86.  Volumetrically.       The    contents    of   the   flask   is 
transferred  to  a  separatory  funnel  and  the  flask  rinsed 
out  several  times  with  ether.     Vigorously  shaking,  the 
acid  layer  is  run  off  and  the  remaining  ethereal  solution 
containing  the  rosin  acids  washed  with  water  until  the 
last  trace  of  acid  is  removed.     Fifty  c.c.  of  alcohol  are 
added,  and  the  solution  titrated  with  standard  caustic 
potash,  using  phenolphthalein  as  an  indicator.     The 
rosin  acids  combine  at  once  with  the  alkali,  whereas 
the  ethylic  esters  remain  unchanged.     The  number  of 
cubic  centimeters  of  normal  alkali  used  multiplied  by 
0.346  will  give  the  amount  of  rosin  in  the  sample. 


46  PAINT  AND  VARNISH  PRODUCTS. 

87.  Gravimetrically.      The   contents  of    the   flask  is 
mixed  with  a  little  petroleum  ether,  boiling  below  80°  C., 
and  transferred  to  a  separating  funnel,  the  flask  being 
washed  out  with  the  same  solvent.     The  petroleum 
ether  layer  should  measure  about  50  c.c.     After  shaking, 
the  acid  solution  is  run  off  and  the  petroleum  ether  layer 
washed  once  with  water,  and  then  treated  in  the  funnel 
with  a  solution  of  0.5  gram  of  potassium  hydroxide  and 
5  c.c.  of  alcohol  in  50  c.c.  of  water.     The  ethylic  esters 
dissolved  in  the  petroleum  ether  will  then  be  found  to 
float  on  top,  the  rosin  acids  having  been  extracted  by 
the  dilute  alkaline  solution  to  form  rosin  soap.     The 
soap  solution  is  then  run  off,  decomposed  with  hydro- 
chloric acid,  and  the  separated  rosin  acids  collected  as 
such,  or  preferably  dissolved  in  ether  and  isolated  after 
evaporating  the  ether.     The  residue,  dried  and  weighed, 
gives  the  amount  of  rosin  in  the  sample. 

88.  Evaporation  test.     This  test  will  show  very  closely 
the  amount  of  benzine  added  along  with  the  drier  in  the 
preparation  of  boiled  linseed  oil. 

Five  grams  of  the  oil  to  be  tested  are  weighed  into 
a  small  flat-bottomed  evaporating  dish  and  allowed 
to  remain  undisturbed  at  a  temperature  of  100°  C. 
for  three  hours.  The  dish  is  then  removed,  cooled 
quickly,  and  immediately  weighed.  The  loss  in  weight 
usually  represents  the  greater  portion  of  mineral  oils, 
rosin  oils,  or  other  volatile  matters  present  in  the 
sample. 

J.  Hortvet,  state  chemist  for  Minnesota,  states  that : 
"Of  fifteen  samples  represented  as  raw  linseed  oil, 
when  subjected  to  this  test,  eleven  showed  no  loss  in 
weight,  while  four  gave  losses  amounting  to  less  than 
0.3  per  cent.  Of  one  hundred  and  ten  samples  repre- 
sented as  boiled  oils,  sixty  gave  losses  above  2  per  cent, 


THE  PURITY  OF  LINSEED  OIL.  47 

thirty-two  showed  no  loss  in  weight,  and  of  the  remain- 
ing eighteen  the  loss  was  slight,  seldom  approaching 
2  per  cent.  Forty-seven  of  the  sixty  samples  which 
gave  over  2  per  cent  loss  were  found  to  vary  in  specific 
gravity  from  0.8835  to  0.9310.  All  samples  not  found 
adulterated  by  the  usual  tests  showed  a  specific  gravity 
of  from  0.9310  to  0.9425,  with  the  exception  of  one 
sample  which  had  a  specific  gravity  as  low  as  0.930, 
but  by  the  other  tests  appeared  to  be  straight  raw  lin- 
seed oil." 

89.  Hexabromide  test.1    The  determination  should  be 
made  in  glass-stoppered  weighing  bottles  about  6  inches 
high  and  1  inch  in  diameter,  weighing  about  30  grams 
each.     These  bottles  should  be   carefully  dried   and 
weighed.     Weigh  0.3  gram  of  oil  to  be  tested,  add 
25  c.c.  of  absolute  ether,  and  cool  to  about  0°  C.     Add 
bromine  drop  by  drop  until  a  considerable  excess  is 
shown  by  the  color  of  the  solution.     Stir  constantly 
during  the  addition,  which  should  be  conducted  very 
slowly,  so  as  to  avoid  heating.     Place  tube  in  ice  water 
for  30  minutes,  then  centrifuge  for  2  minutes.    The  bro- 
minated  oil  is  thrown  to  the  bottom  of  the  tube.     The 
supernatant  liquid  is  quickly  decanted.     Agitate  the 
precipitate  with  10  c.c.  ice-cold  ether  centrifuge  and 
decant ;  repeat  this  procedure  twice,  thoroughly  cooling 
the  precipitate  and  ether  each  time.     Finally  dry  in 
steam  oven  for  30  minutes,  cool,  and  weigh. 

90.  Linseed  oil.  The  following  specifications,  recently 
adopted  by  one  of  the  leading  railroad  companies,  are 
as  comprehensive  as  any  that  have  come  under  the 
author's  observation  and  may  be  regarded  as  typical 
of  those  used  by  discriminating  purchasers  of  linseed 
oil: 

1  Proc.  Am.  Soc.  for  Test.  Mat.,  Vol.  IX,  p.  152. 


48  PAINT  AND  VARNISH  PRODUCTS. 

Material. 

The  material  desired  under  this  specification  is  the 
best  grade  of  raw  and  boiled  linseed  oil,  as  shown  by 
the  following  requirements: 

Raw  Linseed  Oil. 

1.  This  material  must  be  a  good  quality  of  oil  of  a 
pale  yellow  color,  made  from  No.  1  flaxseed,  well  clari- 
fied by  settling  and  age,  and  must  be  unmixed  with 
any  foreign  substance  whatever. 

2.  It  must  not  have  a  greenish  color,  produced  by 
unripe  or  impure  seed. 

3.  Its  specific  gravity  must  be  between  .930  and  .937 
at  60°  F. 

4.  It  must  have  a  flash  above  550°  F.  in  an  open  cup 
tester. 

5.  It  must  contain  less  than  one  per  cent  (1%)  of 
foots. 

6.  It  must  not  lose  more  than  one-tenth  per  cent 
(.1%)  when  heated  at  212°  F.  for  three  hours. 

7.  Its  saponification  value  must  not  be  less  than  187 
or  more  than  195. 

8.  Its  iodine  value  (Hiibrs  Method)  must  exceed 
170. 

9.  It  must  dry  without  tackiness  in  less  than  75 
hours  at  60°  F.  when  a  layer  is  spread  over  a  vertical 
glass  plate  in  uniform  thickness  and  left  in  an  enclosed 
room. 

10.  It  must  not  contain  more  than  one  and  one-half 
per  cent  (1.5%)  of  unsaponifiable  matter. 

11.  Its  acid  value  must  not  exceed  8. 

12.  Its  specific  temperature  reaction  (Thompson  & 
Ballantyne  Method)  must  not  exceed  2.69,  water  =  1 
being  taken  as  the  standard. 


THE  PURITY  OF  LINSEED  OIL.  49 

91.  Boiled  linseed  oil. 

1.  This  material  must  contain  nothing  but  kettle- 
boiled  pure  linseed  oil,  and  lead,  or  manganese  oxides 
or  borates,  or  both,  in  chemical  combination,  but  not 
in  suspension. 

2.  Raw  oil  mixed  with  turpentine  or  benzine  dryer, 
known  as  "Bung  Boiled"  or  " Bung-hole  Boiled"  will 
not  be  accepted. 

3.  Its  specific  gravity  must  be  between  .937  and  .950 
at  60°  F. 

4.  It  must  show  between  two-tenths  per  cent  (.2%) 
and  five-tenths  per  cent  (.5%)  residue  after  ignition. 

5.  The  salts  of  lead  and  manganese  must  not  exceed 
four  per  cent  (4%)  by  weight. 

6.  The  total  weight  of  linseed  oil  in  the  boiled  oil 
must  not  be  less  than  ninety-six  per  cent  (96%). 

7.  It  must  not  show  a  flash  point  below  500°  F.  in  an 
open  cup  tester. 

8.  It  must  not  contain  more  than  one-half  of  one 
per  cent   (.5%)   of  volatile   matter  when   heated   at 
212°  F. 

9.  It  must  not  contain  foots  or  other  suspended 
matter. 

10.  Its  saponification  value  must  exceed  187. 

11.  Its  iodine  value  (Hubl's  Method)  must  exceed 
160. 

12.  Its  acid  value  must  not  exceed  12. 

13.  It  must  dry  without  tackiness  within  24  hours  at 
65°  to  75°  F.  when  a  layer  is  spread  over  a  vertical 
glass  plate  in  uniform  thickness  and  left  in  an  enclosed 
room. 

14.  The  unsaponifiable  organic  matter  must  not  ex- 
ceed two  per  cent  (2%). 

15.  It  must  not  contain  raw  linseed  oil,  mineral  oil, 


50  PAINT  AND  VARNISH  PRODUCTS. 

benzine,  turpentine,  benzene,  rosin,  rosin  oil,  maize  or 
corn  oil,  fish  oil,  cottonseed  oil,  rape  oil,  or  saponifiable 
and  unsaponifiable  oil,  other  than  boiled  linseed  oil. 

92.  Tests.  When  a  shipment  is  received,  a  single 
sample  will  be  taken  from  a  barrel  at  random  and 
the  shipment  will  be  accepted  or  condemned  upon  the 
results  of  the  above  test  Any  standard  test,  in  addi- 
tion to  those  specified  above,  may  be  made  to  ascer- 
tain if  the  shipment  meets  the  intent  and  requirements 
of  this  specification. 

The  above  specifications  require  the  use  of  a  lino- 
leate  drier  in  the  preparation  of  the  boiled  linseed  oil. 
The  author,  however,  can  see  no  serious  objection  to 
the  use  of  a  properly  prepared  non-volatile  resinate 
drier,  as  the  amount  that  may  be  used  cannot  exceed 
4  per  cent,  as  stated  in  section  6. 


CHAPTER  VII. 

ANALYSIS  OF  THE  VOLATILE  OILS. 

93.  Identification.  The  volatile  oil  distilled  from  the 
linseed  oil,  as  previously  described,  may  be  tested  qual- 
itatively for  spirits  of  turpentine,  stump  turpentines, 
rosin  spirit,  petroleum  naphtha,  and  benzole  by  the 
following  test : l 

Shake  in  a  test  tube  equal  volumes  of  the  turpentine 
to  be  tested  and  concentrated  sulphurous  acid  until 
quite  thoroughly  mixed  Set  aside,  noting  the  time 
of  separation  and  the  color  of  the  two  strata.  Samples 
of  known  purity  should  be  run  alongside  of  the  sample 
to  be  tested,  and  the  time  of  shaking  the  samples 
should  be 'as  uniform  as  possible.  Deadwood  turpen- 
tine, if  highly  rectified,  gives  a  reaction  approaching 
that  of  livewood  turpentines. 

1.  American  Turpentine. 

Separation  takes  place  very  slowly. 
Upper  Stratum  —  Opaque;  milky  white. 
Lower  Stratum  —  Translucent;  milky  white. 
Odor  —  Slight  terpene  smell. 

2.  Russian  Turpentine. 

Quick  separation. 

Upper  Stratum  —  Translucent;  faint  turbidity. 

Lower  Stratum  —  Clear  and  colorless. 

Odor  —  Slight  pungent  smell. 

1  Scott's  Test  for  Turpentines,  Drugs,  Oils  and  Paints,  1906. 

51 


52  PAINT  AND  VARNISH  PRODUCTS. 

3.  Deadwood  Turpentine. 

Medium  slow  separation. 
Upper  Stratum  —  Opaque;  light  buff  color. 
Lower  Stratum  —  Translucent ;  yellow-amber  color. 
Odor  —  Distinct  tar  smell. 

4.  Livewood  Turpentine. 

Medium  quick  separation. 

Upper  Stratum  —  Translucent;  lemon-yellow  color. 

Lower  Stratum  —  Clear  and  colorless. 

Odor  —  Mild  tar  smell. 

5.  Rosin  Spirit. 

Medium  slow  separation. 

Upper  Stratum  —  Translucent;  golden-yellow  color. 
Lower  Stratum  —  Translucent;  creamy-white  color. 
Odor  —  Pungent  resin  smell. 

6.  Benzine  (Petroleum  Naphtha). 

Quick  separation. 

Upper  Stratum  —  Clear  and  colorless. 
Lower  Stratum  —  Clear  and  colorless. 
Odor  —  Sulphurous  smell. 

7.  Benzole. 

Quick  separation. 

Upper  Stratum  —  Slight  turbidity;  faint  yellow 

color. 

Lower  Stratum  —  Clear  and  colorless. 
Odor  —  Benzole  and  sulphurous  smell. 

94.  Estimation  of  petroleum  products.  If  the  qualita- 
tive test  indicates  the  presence  of  live  or  deadwood 
turpentine  in  appreciable  quantities,  the  amount  of 


ANALYSIS  OF  THE  VOLATILE  OILS.  53 

petroleum  product  that  may  be  present  is  best  esti- 
mated as  follows: 

A  measured  quantity  of  the  volatile  oil  is  allowed  to 
drop  slowly  into  300  c.c.  of  fuming  nitric  acid  con- 
tained in  a  flask  provided  with  a  return  condenser  and 
immersed  in  cold  water.  A  violent  reaction  takes  place 
and  the  flask  should  be  shaken  occasionally.  When  all 
action  has  ceased  the  contents  of  the  flask  is  poured 
into  a  separatory  funnel  and  thoroughly  washed  with 
successive  portions  of  hot  water  to  remove  the  prod- 
ucts of  the  action  of  the  acid  on  the  turpentine.  The 
remaining  petroleum  oil  is  separated  and  measured  or 
weighed. 

95.  Wood  turpentine  being  absent,  the  amount  of 
petroleum  products  may  be  very  closely  approximated 
by  the  "  Sulphuric  Acid  Number." 

The  apparatus  and  materials  required  are  a  large 
test  tube  of  considerable  diameter,  bedded  in  closely 
packed  cotton,  in  a  fiber  mailing  case  of  suitable  size,  a 
thermometer  provided  with  a  platinum  flange  attached 
to  the  lower  end.  The  lower  part  of  the  flange  is 
bent  at  right  angles  to  the  stem  of  the  thermometer. 
A  mailing  case  packed  with  cotton  offers  many 
advantages  over  the  regulation  asbestos  fiber  mixed 
with  plaster  of  Paris,  in  that  if  the  test  tube  is  broken 
during  the  estimation  the  bottom  of  the  mailing  case 
may  be  readily  removed  and  the  acid-soaked  cotton 
replaced  at  once  with  fresh,  while  the  plaster  of  Paris 
composition  has  to  be  washed  and  dried  out,  an  opera- 
tion requiring  several  hours. 

96.  A  neutral  mineral  oil  is  required,  giving  a  rise 
when  treated  with  sulphuric  acid  of  not  more  than 
3°  C.;  also  a  standard  bottle  of  concentrated  sulphuric 
acid  kept  for  this  purpose,  and  a  sample  of  turpentine 


54  PAINT  AND  VARNISH  PRODUCTS. 

known  to  be  pure.  Fifty  c.c.  of  the  neutral  oil  are 
pipetted  into  the  large  test  tube,  the  temperature  noted, 
and  20  c.c.  of  the  acid,  of  the  same  temperature,  added 
from  the  burette  in  a  steady  stream,  stirring  rapidly, 
meanwhile,  with  a  uniform  motion,  to  maximum  tem- 
perature, which  is  noted.  After  cleaning  and  cooling 
the  apparatus  the  experiment  is  repeated  exactly  as 
before,  but  with  the  addition  of  10  c.c.  of  pure  turpen- 
tine to  the  neutral  oil.  The  rise  in  temperature  is 
again  noted.  Similar  determinations  are  made  with 
mixtures  of  50  per  cent  of  turpentine  and  50  per  cent 
of  benzine,  and  also  of  75  per  cent  of  turpentine  and 
25  per  cent  of  benzine.  Having  thus  ascertained  stand- 
ards for  comparison,  10  c.c.  of  the  sample  under  exam- 
ination is  carried  through  in  exactly  the  same  manner, 
the  maximum  temperature  noted,  and  the  per  cent  of 
turpentine  and  of  petroleum  product  calculated.  Com- 
mercially pure  turpentines  will  give  closely  uniform 
results.  Wood  turpentines  give  lower  figures,  which 
approach  those  of  turpentine  the  more  carefully  the 
product  is  prepared  and  purified.  Rosin  spirits  give  a 
rise  of  7°  to  10°  C.,  benzine  and  benzole  3°  to  8°  C. 

97.  Determination  of  flash  point  and  fire  test  of  petro- 
leum products,  turpentine,  etc.  Covered  testers.  New 
York  State  Board  of  Health  Tester.  This  instrument 
consists  of  a  copper  oil  cup  holding  about  10  ounces 
heated  in  a  water  bath  over  a  small  flame.  The  cup  is 
provided  with  a  glass  cover  holding  a  thermometer. 
This  cover  also  has  a  hold  for  the  insertion  of  the  test- 
ing flame. 

The  test  should  be  applied  as  follows:1 

"  Remove  the  oil  cup  and  fill  the  water  bath  with 
cold  water  up  to  the  mark  on  the  inside.  Replace  the 
1  Report  New  York  State  Board  of  Health,  1882,  p.  495. 


ANALYSIS   OF  THE  VOLATILE  OILS. 


55 


oil  cup  and  pour  in  enough  oil  to  fill  it  to  within  one- 
eighth  of  an  inch  of  the  flange  joining  the  cup  and  the 
vapor  chamber  above.  Care  must  be  taken  that  the 
oil  does  not  flow  over  the  flange.  Remove  all  air 
bubbles  with  a  piece  of  dry  paper.  Place  the  glass  cover 
on  the  oil  cup,  and  so  adjust  the  thermometer  that  its 
bulb  shall  be  just  covered  by  the  oil. 

"If  an  alcohol  lamp  be  employed  for  heating  the 
water  bath  the  wick  should  be  carefully  trimmed  and 
adjusted  to  a  small  flame.  A  small  Bunsen  burner  may 
be  used  in  place  of  the  lamp.  The  rate  of  heating 
should  be  about  two  degrees  per  minute,  and  in  no  case 
should  exceed  three  degrees. 

"As  a  flash  torch,  a  small  gas  jet  one-quarter  of  an 
inch  in  length  should  be  employed.  When  gas  is  not 
at  hand  employ  a  piece  of  waxed-linen  twine.  The 
flame  in  this  case,  however,  should  be  small. 

98.  ANALYSIS  OF  VOLATILE  OILS  BY  THE  AUTHOR. 


No. 

Name  of 
Oil. 

Sp.  Gr. 
at22°C. 

Odor. 

Rise 
C. 

Separation. 

Lower 
Layer. 

Upper  Layer. 

2 
3 

Terraben- 
tine 
Turpentine 

Turpentine 

.808 
.855 

.862 

Petroleum 
Camphor 

Oil 

6° 
52.5° 

57.0° 

Immediate 
Rapid 

Medium 

Clear 
Almost 
clear 
Milky 

Slightly  milky 
Lemon,  milky 

4 
5 

Off-color 
turpentine 
Turpentine 

.857 
.853 

Characteristic 
turpentine 

30.5° 
48.3° 

Slow 
Slow 

Clear 
Milky 

Clear 
Milky 

6 

7 

Turpentine 

Wood-spirits 
turpentine 

.860 
.859 

Stump  tur- 
pentine 

56.7° 
52.8° 

Medium 
Slow 

Milky 

Deep 
lemon 

Slight  tinge  of 
yellow 

Milky 

8 

Turpanli 
base 

.862 

Petroleum 

1.0° 

Quick 

Clear 

Clear 

No.  1.  Straight  petroleum  product. 

No.  2.  Wood  turpentine. 

No.  3.  Commercially  pure  turpentine. 

No.  4.  Spirits  of  turpentine,  containing  about  50  per  cent  petroleum  naphtha. 

No.  5.  Spirits  of  turpentine,  containing  about  15  per  cent  petroleum  naphtha. 

No.  6.  Poorly  rectified  turpentine. 

No.  7.  Stump  turpentine. 

No.  8.  Straight  petroleum  product. 


56  PAINT  AND  VARNISH  PRODUCTS. 

99.  "When  the  temperature  of  the  oil  in  the  case 
of  kerosene  has  reached  85°  F.,  the   testings  should 
begin.     To  this  end  insert  the  torch  into  the  opening 
in  the  cover,  passing  it  in  at  such  an  angle  as  to  well 
clear  the  cover,  and  to  a  distance  about  half-way  be- 
tween the  oil  and  the  cover.     The  motion  should  be 
steady  and  uniform,  rapid,  and  without   any  pause. 
This  should  be  repeated  at  every  two  degrees'  rise  of 
the  thermometer,  until  the  thermometer  has  reached 
95  degrees,  when  the  lamp  should  be  removed  and  the 
testings  should  be  made  for  each  degree  of  temperature 
until  100  degrees  is  reached.     After  this  the  lamp  may 
be  replaced  if  necessary,  and  the  testings  continued  for 
each  two  degrees. 

"The  appearance  of  a  slight  bluish  flame  shows  that 
the  flashing  point  has  been  reached. 

"In  every  case  note  the  temperature  of  the  oil  before 
introducing  the  torch.  The  flame  of  the  torch  must 
not  come  in  contact  with  the  oil. 

"The  water  bath  should  be  filled  with  cold  water  for 
each  separate  test,  and  the  oil  from  a  previous  test  care- 
fully wiped  from  the  oil  cup." 

100.  Open  testers.    Tagliabue's  open  tester.     This  in- 
strument is  similar  to  the  preceding,  except  that  it  is 
smaller,  the  oil  cup  being  of  glass  and  without  a  cover. 
The  water  bath  is  filled  as  before.     The  oil  cup  is  filled 
to  within  three  thirty-seconds  of  an  inch  of  the  top. 
The  heating  flame  is  regulated  to  three-fourths  of  an  inch 
in  height,  or  to  such  a  height  that  the  temperature  of 
the  oil  is  raised  two  and  a  half  degrees  per  minute  until 
97°  F.  is  reached,  when  the  test  flame  is  applied  and 
the  testings  are  made  every  two  degrees  until  the  flash 
point  is  reached. 

101.  Fire  test.    The  fire  test  is  the  temperature  at 


ANALYSIS  OF  THE  VOLATILE  OILS.  57 

which  an  oil  will  give  off  vapors  which  when  ignited 
will  burn  continuously.  The  cover  is  removed  in  the 
.case  of  the  closed  tester,  the  heating  being  continued  as 
described  above.  The  flame  may  be  extinguished  by 
the  use  of  a  piece  of  asbestos  board. 

102.  Excessive  use  of  volatile  oils.     An  excess  of  thin- 
ners  or  volatile  oils  is  detrimental  to  the  life  of  the  paint. 
Sabin  in  his  work  on  The  Technology  of  Paint  and 
Varnish  writes  as  follows : 

"Most  of  the  failures  of  lead  and  zinc  paints  are  due 
to  the  use  of  these  volatile  thinners  (turpentine  and 
benzine).  If  raw  linseed  oil  is  used,  it  may  be  desir- 
able to  add  5  per  cent  of  a  good  drier.  This  should  be 
pale  in  color,  indicating  that  it  has  been  made  at  a  low 
temperature,  and  should  be  free  from  rosin.  The  latter 
is  not  an  easy  thing  to  detect,  but  if  a  fair  price  is  paid, 
say  $1.50  to  $2.00  a  gallon  at  retail,  and  freedom  from 
rosin  is  guaranteed  by  a  maker  of  good  reputation,  the 
buyer  ought  to  feel  safe." 

103.  The  presence  of  a  large  amount  of  thinners  ren- 
ders the  paint  easier  to  brush  out,  and  hence  the  tend- 
ency has   been  to  increase  the  amount   of  thinners, 
especially  benzine,  because  of  its  low  cost,  in  mixed 
paints,  resulting  in  the  reducing  of  the  linseed  oil  to  a 
percentage  below  that  required  to  give  the  proper  life 
to  the  paint.     The  better  class  of  paint  manufacturers 
seem  to  consider  4  to  9  per  cent  of  thinners  sufficient 
for  outside  house  paints. 

Excluding  the  21  paints  containing  12  per  cent  of 
thinners  and  over,  the  average  amount  of  thinners  in 
the  remaining  50  paints  was  7.3  per  cent.  The  paints 
high  in  thinners  were  in  almost  every  case  inferior 
paints,  high  in  inert  pigments. 

Of  seventy-one  analyses  of  white  and  gray  mixed 


58  PAINT  AND  VARNISH  PRODUCTS. 

paints  made  by  the  author,  the  amount  of  thinners  came 
between  the  following  limits : 


Pe 

Th 

0 

r  cent 
inners. 

to    4 

Number  of 
Paints. 

...                   6 

4 

"    5  

5 

5 

"6 

1 

6 

"    7  

6 

7 

"8                 

10 

8 

"    9  

5 

q 

"10      

11 

10 

"11  

4 

11 

"12  

2 

12 

"  29. 

21 

CHAPTER  VIII. 

TURPENTINE  THINNERS. 

104.  Spirits  of  Turpentine.     This  product,  which  has 
long  been  known  to  the  paint  and  varnish  trade,  pos- 
sesses several  commercial  designations,  such  as  "gum 
turpentine,"  "oil   of   turpentine,"   "turpentine,"  and 
"spirits   of  turpentine."     Its   source   and   distinctive 
properties  are  specifically  set  forth  in  the  Pharmaco- 
poeia of  the  United  States  as  follows:  "Oil  of  turpen- 
tine :  A  volatile  oil  distilled  from  turpentine  (a  concrete 
oleo-resin  obtained  from  Pinus  palustris  and  other  spe- 
cies of  pinus)."    "A  thin,  colorless  liquid  having  a  char- 
acteristic odor  and  taste."     "Specific  gravity  0.855  to 
0.870  at  15°  C:  (59°  F.).     It  boils  at  155°  to  170°  C. 
(311°  to   338°  F.)."     The  United  States  Government 
under  the  Food  and  Drugs  Act  has  ruled  that  a  product 
to  be  entitled  to  the  above  designations  —  "spirits  of 
turpentine,"  "turpentine,"  etc., — must  comply  with 
the  pharmacopceial  requirements  above  stated,  and  that 
oils  obtained  by  distillation  from  resinous  woods  should 
be  designated  "wood"  or  "stump"  turpentine. 

105.  Adulteration.     The   paint   or   varnish   manufac- 
turer who  purchases  direct  from  dealers  engaged  in  the 
naval  stores  business  will  very  rarely  receive  willfully 
adulterated  turpentine,  but  will   occasionally  receive 
shipments  of  insufficiently  refined  turpentine  contain- 
ing various  quantities  of  rosin  and  resinous  matters. 
This  form  of  adulteration  is  easily  detected.     On  the 
other  hand,  the  retail  dealer  and  master  painter  who 
purchase  from  jobbing  houses  and  traveling  salesmen 

59 


60  PAINT  AND  VARNISH  PRODUCTS. 

are  very  liable  to  obtain  an  adulterated  article.  Recent 
investigations  have  shown  that  the  adulteration  of  tur- 
pentine after  it  has  been  shipped  from  the  primary 
markets  is  a  much  more  common  practice  than  has 
been  supposed.  Usually  the  adulteration  has  been  ac- 
complished with  naphtha  or  other  petroleum  distillates, 
which,  owing  to  their  low  price,  makes  this  phase  of  the 
industry  very  profitable.  The  author  believes  that  the 
adulteration  of  turpentine  with  rosin  spirit  or  with 
wood  turpentine  is  very  rare,  as  the  margin  of  profit  is 
not  large  enough  to  make  the  proposition  sufficiently 
attractive. 

1 06.  Specifications.  The  specifications  adopted  by  the 
Navy  Department  Jan.  4,  1908,  for  spirits  of  turpen- 
tine are  as  complete  as  any  that  have  come  under  the 
observation  of  the  author: 

1.  The  turpentine  must  be  the  properly  prepared  dis- 
tillate of  the  resinous  exudation  of  the  proper  kinds  of 
live  pine  or  live  pitch  pine,  unmixed  with  any  other 
substance;  it  must  be  pure,  sweet,  clear,  and  white,  and 
must  have  characteristic  odor. 

2.  A  single  drop  allowed  to  fall  on  white  paper  must 
completely  evaporate  at  a  temperature  of  70°  F.  with- 
out leaving  a  stain. 

3.  The  specific  gravity  must  not  be  less  than  0.862 
or  greater  than  0.872  at  a  temperature  of  60°  F. 

4.  When  subjected  to  distillation,  not  less  than  95 
per  cent  of  the  liquid  should  pass  over  between  the 
temperature  of  308°  F.  and  330°  F.,  and  the  residue 
should  show  nothing  but  the  heavier  ingredients  of 
pure  spirits  of  turpentine.     If  at  the  beginning  of  the 
operation  it  shows  a  distillation  point  lower  than  305°  F. 
this  will  constitute  a  cause  for  rejection. 

5.  A  definite  quantity  of  the  turpentine  is  to  be  put 


TURPENTINE  THINNERS.  61 

in  an  open  dish  to  evaporate,  and  the  temperature  of 
the  dish  will  be  maintained  at  212°  F.;  if  a  residue 
greater  than  2  per  cent  of  the  quantity  remains  on  the 
dish  it  will  constitute  a  cause  for  rejection. 

107.  Flash  tests.     An  open  tester  is  to  be  filled  within 
one-fourth  inch  of  its  rim  with  the  turpentine,  which 
may  be  drawn  at  will  from  any  one  can  of  the  lot 
offered  under  the  proposal.     The  tester  thus  filled  will 
be  floated  on  water  contained  in  a  metal  receptacle. 
The  temperature  of  the  water  will  be  gradually  and 
steadily  raised  from  its  normal  temperature  of  about 
60°  F.  by  applying  a  gas  or  spirit  flame  under  the  re- 
ceptacle.    The  temperature  of  the  water  is  to  be  in- 
creased at  the  uniform  rate  of  2°  F.  per  minute.     The 
taper  should  consist  of  a  fine  linen  or  cotton  twine 
(which  burns  with  a  steady  flame)  unsaturated  with  any 
substance.     When  lighted  it  is  to  be  used  at  every 
increase  of  1  degree  temperature,  beginning  at  100°  F. 
It  is  to  be  drawn  horizontally  over  the  surface  of  the 
turpentine  and  on  a  level  with  the  rim  of  the  tester. 
The  temperature  will  be  determined  by  placing  a  ther- 
mometer, in  the  turpentine  contained  in  the  tester  so 
that  the  bulb  will  be  wholly  immersed  in  the  liquid. 
The  turpentine  must  not  flash  below  105°  F. 

1 08.  Sulphuric  acid  test.     Into  a  30  c.c.  tube,  gradu- 
ated to  tenths,  put  6  c.c.  of  the  spirits  of  turpentine  to 
be  examined.     Hold  the  tube  under  the  spigot  and  then 
slowly  fill  it  nearly  to  the  top  of  the  graduation  with 
concentrated  oil  of  vitriol.     Allow  the  whole  mass  to 
become  cool  and   then  cork   the   tube  and  mix   by 
shaking  the  tube  well,  cooling  with  water  during  the 
operation  if  necessary.     Set  the  tube  vertical  and  allow 
it  to  stand  at  the  ordinary  temperature  of  the  room 
not  less  than  half  an  hour.     The  amount  of  clear  layer 


62  PAINT  AND  VARNISH  PRODUCTS. 

above  the  mass  shows  whether  the  material  passes  test 
or  not.  If  more  than  6  per  cent  of  the  material  re- 
mains undissolved  in  the  acid  this  will  constitute  a 
cause  for  rejection. 

109.  Adulteration  with  petroleum  products.  Adulter- 
ation with  any  considerable  quantity  of  a  petroleum 
distillate  will  be  indicated  by  a  low  specific  gravity  of 
the  suspected  sample,  but  if  10  per  cent  or  less  be 
present  the  gravity  will  be  lowered  only  slightly  and 
distillation  through  a  LeBel-Hennirger  column  should 
be  resorted  to  and  the  specific  gravity  and  index  of 
refraction  of  the  different  fractions  should  be  deter- 
mined as  described  in  the  paragraphs  devoted  to  wood 
turpentine  in  this  chapter.  The  rise  of  temperature 
with  sulphuric  acid,  of  the  different  fractions  as  de- 
scribed in  the  preceding  chapter,  will  give  an  approxi- 
mation of  the  amount  of  petroleum  distillate  present. 

If  adulteration  with  wood  turpentine  be  suspected, 
the  quantity  and  character  of  the  heavier  fractions 
should  be  carefully  determined. 

no.  Rosin  spirit.  If  rosin  spirit  is  suspected,  the  test 
proposed  by  Grimaldi  may  be  made  use  of.  Distill 
100  c.c.  of  the  oil  of  turpentine  to  be  examined  over  a 
very  small  gas  flame,  and  collect  the  fractions  separately 
at  intervals  of  5  degrees  of  temperature.  To  the  first 
five  fractions  an  equal  volume  of  hydrochloric  acid  is 
added,  and  a  few  granules  of  pure  tin,  and  the  whole 
well  shaken  and  kept  in  a  water  bath  for  five  minutes. 
The  presence  of  resin  spirit  (pinolin)  is  indicated  by  a 
green  color,  which  varies  according  to  the  percentage 
of  resin  spirit  present.  Further,  one  drop  of  each 
fraction  is  tested  by  mixing  with  2  c.c.  of  Halphen's 
reagent  (sulphur  dissolved  in  carbon  disulphide)  and  a 
little  melted  phenol  dissolved  in  carbon  tetrachloride. 


TURPENTINE  THINNERS.  63 

A  trace  of  bromine  vapor  is  allowed  to  fall  on  the 
liquid,  and  in  the  presence  of  resin  spirit  a  green  color 
will  develop  within  half  a  minute. 

in.  Wood  turpentine.  The  use  of  wood  turpentine 
is  increasing  rapidly.  The  different  products  offered 
under  this  heading  are  of  a  much  more  satisfactory  na- 
ture than  those  offered  for  sale  a  few  years  ago.  This 
improvement  in  quality  is  due  to  increased  care  in  refin- 
ing, thereby  eliminating  the  objectionable  impurities. 
As  these  wood  turpentines  are  offered  for  sale  at  a 
price  of  from  2  to  10  cents  below  that  of  gum  spirits, 
it  is  distinctly  to  the  advantage  of  the  manufacturer  of 
paints  and  varnishes  to  use  them,  provided  he  can 
secure  a  well-refined  article.  Unfortunately,  while  the 
producers  of  wood  turpentine  are  many,  the  amount 
produced  by  any  one  company  is  comparatively  small, 
and  it  is  usually  impossible  for  a  paint  manufacturer 
to  secure  a  steady  and  uniform  source  of  supply.  It 
therefore  devolves  upon  the  paint  chemist  to  examine 
a  considerable  number  of  wood  turpentines  yearly,  and 
to  select  those  best  suited  for  the  purpose,  or,  in  other 
words,  to  select  those  which  more  nearly  resemble  the 
gum  spirits. 

112.  As  is  well  known,  wood  turpentine  is  obtained  by 
two  methods,  viz.,  by  subjecting  the  stumps  or  mill 
waste  to  a  destructive  distillation,  whereby  the  turpen- 
tine obtained  is  contaminated  with  the  decomposition 
products  from  the  breaking  down  of  the  rosin  and  the 
wood,  which  renders  the  refining  of  the  turpentine  a 
very  difficult  matter.  In  fact,  a  paint  manufacturer 
will  usually  discriminate  against  a  turpentine  obtained 
by  destructive  distillation.  The  other  process  of  ob- 
taining wood  turpentine  is  by  steaming  the  chipped 
stumps  or  mill  waste,  thereby  avoiding  any  serious 


64  PAINT  AND  VARNISH  PRODUCTS. 

decomposition  of  the  wood  or  rosin  contained  in  it. 
On  redistillation  a  turpentine  product  is  obtained  which 
has  a  pleasant  odor,  suggestive  of  pine  wood,  and  which 
will  distill  largely  within  the  accepted  limits  of  the  ordi- 
nary gum  spirits,  but  which  will  contain  a  varying 
fraction  of  the  heavier  pine  oils. 

113.  A  suitably  selected  " Steam"  turpentine  is  fully 
the  equal  of  the  gum  spirits  for  mixed  paints  and  for 
medium  or  slow-drying  varnishes.  For  such  quick 
drying  varnishes  as  it  is  desirable  to  prepare  with  the 
aid  of  turpentine  alone  or  with  naphtha,  a  mixture  of 
40  per  cent  of  gum  spirits  with  60  per  cent  of  a  steam 
wood  turpentine  is  as  desirable  as  the  gum  spirits 
alone. 

.  114.  Valuation  of  wood  turpentine.  The  valuation  of 
a  wood  turpentine  aside  from  its  odor  will  depend 
largely  upon  its  distillation  figures  and  the  specific 
gravities  of  the  fractions  obtained.  The  more  usual 
method  of  distilling  with  the  aid  of  direct  heat  in  a 
side-necked  distilling  flask  is  open  to  serious  objection 
for  two  reasons:  first,  the  portions  that  condense  in 
the  neck  of  the  flask  and  drop  down  on  the  hot  liquid 
below  will  cause  a  certain  amount  of  " cracking"  or 
decomposition,  coloring  the  undistilled  residue  yellow; 
second,  when  only  a  small  amount  remains  in  the  dis- 
tilling flask  the  vapors  become  superheated,  which 
may  indicate  a  distilling  temperature  several  degrees 
above  the  normal  figure.  Under  the  same  conditions 
pure  water  can  be  made  to  indicate  a  distilling  tempera- 
ture of  as  high  as  107°  C.,  due  to  the  superheating  of 
the  aqueous  vapor. 

115.  Distillation  with  steam.  The  most  satisfactory 
method  of  conducting  the  distillation  is  to  use  steam, 
and  thus  avoid  direct  heating  altogether.  By  the  use 


TURPENTINE  THINNERS.  65 

of  a  LeBel-Henninger  5-bulb  distilling  tube  or  column 
the  heavier  fractions  in  the  turpentine  can  readily  be 
separated  and  their  gravities  examined,  and  the  non- 
volatile residue  can  be  examined  as  to  color  and  per- 
centage. 

1 1 6.  Author's  modification.    Three  hundred  cubic  cen- 
timeters of  the  sample  to  be  examined  are  placed  in 
a  500  c.c.  Erlenmeyer  flask  provided  with  a  5-bulb 
LeBel-Henninger  column  and  with  a  steam  supply  tube 
extending  nearly  to  the  bottom  of  the  flask.     The  con- 
tents of  the  flask  are  raised  by  direct  heat  to  about 
80  or  90°  C.    The  source  of  heat  is  then  removed  and 
live  steam  admitted,  the  distillate  being  collected  in  a 
100  c.c.  graduated  cylinder,  which  is  changed  as  soon 
as  the  100  c.c.  mark  is  reached.     This  operation  is 
continued  until  all  the  volatile  portions  have  distilled 
over,  and  the  number  of  cubic  centimeters  of  turpen- 
tine and  of  water  in  each  100  c.c.  cylinder  is  then 
noted. 

117.  Law  governing  distillation  of   mutually   insoluble 
liquids.     In  the  distillation  of  a  mixture  of  two  mutu- 
ally insoluble  liquids,  each  of  which  has  a  definite  boil- 

"ing  point,  it  is  a  well-known  fact  that  the  mixture  will 
distill  at  a  constant  temperature,  in  the  ratio  of  the 
products  of  their  respective  vapor  densities  and  vapor 
tensions,  at  the  temperature  of  distillation.  In  the 
above  case,  when  we  have  a  mixture  of  water  and  gum 
turpentine,  the  ratio  of  distillation  is  approximately  60 
parts  of  turpentine  to  40  parts  of  water,  the  distilling 
temperature  being  about  94°  C.  This  ratio  holds  only 
for  that  portion  of  the  turpentine  which  distills  with 
direct  heat  between  156°  C.  and  160°  C.  The  heavier 
fractions  require  a  much  larger  volume  of  water  for 
their  distillation. 


66 


PAINT  AND  VARNISH  PRODUCTS. 


118.  Distillation  figures  of  a  gum  turpentine.  The  fol- 
lowing table  illustrates  the  distillation  results  obtained 
with  a  gum  turpentine  slightly  below  average: 


Fraction. 

Mixed  Distillate. 

Turpentine. 

Water. 

Temperature. 

Sp.  Gravity 
at22°C. 

c.c. 

c.c. 

c.c. 

Deg.  C. 

1 

100 

60 

40 

94 

0.862 

2 

100 

60 

40 

94.5 

0.862 

3 

100 

60 

40 

94.5 

0.862 

4 
5 

50 
50 

30 
29 

20 
21 

94.51 
95.  0/ 

0.866 

6 

50 

25 

25 

95.5 

0.867 

7 

50 

18 

32 

97.0 

0.871 

8 

100 

12 

88 

97.5-98.5 

9 

Non-  volatile 

6 

119.  Distillation  figures  of  a  wood  turpentine.  A  wood 
turpentine  under  similar  treatment  gave  the  following 
results: 


Fraction. 

Mixed  Distillate. 

Turpentine. 

Water. 

Tempera- 
ture. 

Specific  Grav- 
ity at  22°  C. 

c.c. 

c.c. 

c.c. 

Deg.  C. 

1 

100 

60 

40 

94.0 

0.8600 

2 

100 

60 

40 

94.5 

0.8605 

3 

100 

60 

40 

95.0 

0.8610 

4 

100 

60 

40 

95.0 

0.8610 

5 

100 

58 

42 

95.5 

0.8615 

6 

100 

47 

53 

96.0 

0.8620 

7 

50 

20 

30 

96.5 

0.866 

8 

50 

15 

35 

97.0 

0.872 

9 
10 

50 
50 

10 
3 

40 

47 

98.0  ) 
98.5J 

0.885 

11 

Non-volatile 

7 

Fraction  No.  8  was  of  a  straw  color  and  Nos.  9  and 
10  were  yellow.  This  particular  sample  represented  a 
rather  high  grade  of  a  destructively  distilled  wood 
turpentine. 

120.  In  order  to  conduct  the  distillation  successfully 
and  rapidly  the  apparatus  required  should  always  be 
kept  set  up  ready  for  use.  The  specific  gravities  can 


TURPENTINE  THINNERS.  67 

readily  be  determined  with  a  Westphal  balance,  and  it 
will  be  found  that  the  entire  operation  can  be  con- 
ducted in  the  same  length  of  time  as  is  required  for 
the  more  ordinary  distillation.  This  method  thor- 
oughly differentiates  the  heavier  fractions  and  leaves 
the  residue  uncontaminated  with  decomposition  prod- 
ucts such  as  are  obtained  when  direct  heat  is  applied. 
It  is  of  course  understood  that  the  distillations  should 
always  be  conducted  under  uniform  conditions. 

121.  Detection  of  petroleum  products.    If  there  is  any 
reason  to  suspect  adulteration  with  petroleum  products, 
such  as  benzine,  petroleum  spirits,  or  kerosene,  the  de- 
termination of  the  index  of  refraction  of  the  different 
fractions  and  the  rise  of  temperature  with  sulphuric 
acid  will  reveal  even  a  very  small  percentage  of  adul- 
teration. 

122.  Geer's  modification.    In  cases  of  controversy  or 
in  court  procedure,  the  modification  worked  out  by 
Geer  (U.  S.  Dept.  of  Agriculture,  Forest  Service,  Circu- 
lar 152),  which  is  somewhat  similar  to  the  author 's 
method,  may  be  followed  to  advantage,  as  it  is  more 
elaborate  and  specific  in  its  details.     For  ordinary  com- 
mercial usage,  however,  it  is  somewhat  lengthy  and 
tedious  in  its  application. 

123.  Standards  of  purity.     It  is  well-nigh  impossible 
to  establish  standards  with  regard  to  the  amount  of 
non-volatile  matter  permissible  in  a  high-grade  gum 
turpentine  or  of  a  heavy  turpentine  and  non-volatile 
matter  permissible  in  wood  turpentine.     The  author  has 
rejected  numerous  samples  of  gum  turpentine  contain- 
ing non- volatile  matters  in  excess  of  1.8  per  cent,  as  the 
non-volatile  matter  was  of  a  distinctly  resinous  nature. 
In  a  wood  turpentine  the  non-volatile  matter  should 
not  exceed  2  per  cent,  nor  contain  more  than  10  per 


68  PAINT  AND  VARNISH  PRODUCTS. 

cent  of  a  fractionated  portion  with  specific  gravity 
above  0.872.  Usually  each  paint  chemist  will  estab- 
lish his  own  standards,  based  on  his  own  experience. 
He  should,  however,  keep  for  future  reference  a  pint 
sample  of  each  distinctive  turpentine  examined.  These 
should  be  kept  in  a  tightly  closed  can  or  in  a  bottle 
which  has  received  a  heavy  coating  of  black  paint  in 
order  to  avoid  the  chemical  changes  caused  by  light. 
A  variety  of  such  samples,  together  with  the  data  apper- 
taining to  them,  color,  odor,  flash  point,  gravity,  and 
distillation  figures,  including  the  specific  gravities  of  the 
fractions  and  their  indices  of  refraction,  will  enable  the 
chemist  to  pass  on,  or  place  a  comparative  valuation  on, 
any  given  sample  rapidly  and  accurately. 

124.  The  heavier  turpentines.     In  the  production  of 
wood  turpentine  by  steaming  or  by  extraction  a  series 
of   heavier   terpene   bodies   are   obtained.     In   some 
instances  these  are  allowed  to  remain  in  the  turpen- 
tine, and  of  course  are  readily  detected  and  estimated 
by  the  fractionating  method  above  described.     Gen- 
erally these  terpenes  are  removed  to  a  certain  extent 
by  the  producer  and  placed  on  the  market  under  some 
such  name  as  pine  oil.     Like  the  wood  turpentines 
found  on  the  market  several  years  ago,  they  differ 
greatly  in  value  and  desirability,  no  uniform  standard 
having  been  established.     The  more  desirable  varieties 
have  a  mild,  pleasant,  fragrant  pine  odor,  somewhat 
suggestive  of  camphor,  and  a  specific  gravity  varying 
between  0.890  and  0.925.     The  heavier  varieties,  0.925 
to  0.940,  are  not  so  desirable  for  paint  or  varnish  pur- 
poses, owing  to  their  less  pleasant  odor  and  compara- 
tively slight  volatility. 

125.  Correct  designation.     The  name   "pine  oil"   as 
applied  to  these  terpenes  is,  in  the  opinion  of  the  author, 


TURPENTINE  THINNERS.  69 

somewhat  of  a  misnomer,  and  a  name  like  "  heavy  tur- 
pentine "  is  much  more  applicable,  as  these  bodies 
very  closely  resemble  the  ordinary  turpentine  in  their 
properties  and  show  little  analogy  to  the  fixed  or  non- 
volatile oils,  or  to  the  rosin  oil,  except  those  fractions 
having  a  gravity  of  upwards  of  0.940. 

126.  Properties.    A  desirable  " heavy  turpentine"  is 
completely  volatile,  without  leaving  an  oily  stain,  in 
about  6  hours,  when  3  drops  are  allowed  to  fall  on  the 
same  spot  on  a  sheet  of  ordinary  filter  paper.     When 
used  with  linseed  oil  such  a  turpentine  acts  as  a  true 
drier,  and  in  this  respect  is  even  superior  to  ordinary 
turpentine.    As  its  rate  of  evaporation  from  the  oil  or 
paint  film  is  much  slower,  its  effect  is  exerted  for  a 
much  greater  length  of  time.     This  can  readily  be 
demonstrated  by  placing  on  a  sheet  of  glass  some  raw 
linseed  oil,  a  mixture  of  90  parts  of  linseed  oil  to  10  of 
turpentine,  and  90  parts  of  linseed  oil  to  10  of  heavy 
turpentine;  then  placing  the  sheet  of  glass  at  an  angle 
of   about   30    degrees    from    the    perpendicular    and 
noting  the  rate  of  drying.     For  ready  mixed  paints 
for  outside  use  and  for  liquid  driers  for  the  store  and 
manufacturing  trades,  the  heavy  turpentines  offer  great 
possibilities,  as  these  turpentines  can  be  obtained  for 
from  10  to  15  cents  below  gum  turpentine,  and  by  reason 
of  their  great  drying  strength  permit  the  use  of  con- 
siderable quantities  of  naphtha  for  thinning  to  suitable 
consistency. 

127.  Value  as  a  drier.    It  is  quite  generally  conceded 
that  one  of  the  causes  of  the  ultimate  breaking  down 
of  linseed-oil  paints  is  the  fact  that  the  metallic  driers 
used  to  hasten  the  drying  of  the  linseed  oil  do  not 
cease  their  action  on  accomplishing  the  drying  of  the 
paint  film,  but  continue  their  oxidizing  action,  slowly 


70  PAINT  AND  VARNISH  PRODUCTS. 

but  nevertheless  surely,  converting  the  dry  but  elastic 
oil  film,  or  linoxyn,  into  a  brittle,  non-elastic  substance, 
which,  having  lost  its  life  or  binding  strength,  readily 
crumbles  and  disintegrates.  The  greater  the  extent  to 
which  metallic  driers  can  be  avoided  and  yet  secure 
proper  drying  of  the  paint,  the  longer  the  life  of  the 
paint.  A  drier  composed  of  naphtha,  heavy  turpen- 
tine, and  a  small  quantity  of  resinate  or  linoleate  drier 
affords  a  product  much  superior  to  the  medium  or  low- 
priced  driers  on  the  market.  The  same  reasons  hold 
good  for  the  use  of  the  heavy  turpentines  in  outside 
mixed  paints. 

128.  Use  in  varnishes.     In  quick-drying  varnish  prod- 
ucts and  paints  the  use  of  a  drier  is  not  advantageous 
except  in  special  cases.     It  is  possible  to  make  extremely 
short  oil  varnishes,  6  to  7  gallons  of  oil  per  100  Ibs.  of 
gum,  by  starting  the  thinning  at  450°  F.  to  480°  F.  with 
a  heavy  turpentine  of  specific  gravity  of  about  0.910, 
using  about  2  gallons  or  just  a  sufficient  amount  to 
reduce  the  temperature  of  the  kettle  to  the  point  of 
safety   for  the   addition   of   turpentine   or  petroleum 
spirits  for  the  completion  of  the  thinning.     If  added 
promptly  it  will  save  a  kettle  of  varnish  that  has  begun 
to  curdle  in  the  initial  stage  of  thinning  from  lack  of 
sufficient  heat  or  other  causes. 

129.  Standard  of  purity.    As  before  stated,  the  heavy 
turpentines  should  be  selected  with  regard  to  freedom 
from  material  percentages  of  fractions  heavier  than  0.930. 
Also,  as  some  of  the  largest  producers  of  these  oils  obtain 
their  products  with  the  aid  of  a  petroleum  solvent,  the 
presence  of  mineral  oils  must  be  looked  for,  which  if 
present  in  quantity  will  leave  a  greasy  stain  on  paper. 
As  the  boiling  point  of  a  heavy  turpentine  will  be  be- 
tween 190°  C.  and  225°  C.,  distillation  with  direct  heat 


TURPENTINE  THINNERS.  71 

will  cause  a  certain  amount  of  decomposition,  especially 
of  the  heavier  fractions,  and  distillation  at  100°  C.  with 
steam  through  a  LeBel-Henninger  column  results  in  a 
very  slow  distillation,  about  15  c.c.  of  turpentine  to 
85  c.c.  of  water.  It  will  be  found  advisable  to  heat  the 
distilling  flask  in  a  paraffine  oil  bath  to  160°  C.,  and 
while  maintaining  this  temperature  with  care,  pass  a 
current  of  steam  through  the  heated  turpentine,  dis- 
till, and  examine  the  fractions  as  above  outlined  with 
special  reference  to  the  index  of  refraction. 

Polymerization  with  sulphuric  acid  does  not  yield 
satisfactory  results,  as  a  considerable  percentage  re- 
mains unacted  upon. 


CHAPTER   IX. 


A  word  may 

be  said  in  i  •*!•?*  ^m  with,  the  increased  use  of  volatile 
products  as  paint  thinness*    In  discussing 

theprob- 


or  in  part  the  luiprntiatl 


of  turpentine  substitutes, 
the  exact  function  erf  the 
to  prepare  an 
prapevtaa 
tune  be  free  from  objectionable  char- 
to  the  views 
of  the 


73 


to  produce  a  "flat"  or  "semi-flat"  surface, 

ance,  as  in  the  ease  of  paints  intended  for  inside  we; 
to  lender  the  paint  more  fluid  without  the  use  of  an 

- ..._,..-. 4-   *jt    ,.t| j       -          *IL  ,    , .„  .  .  _;    .  :    ~\  ~ 

excess  ve  amount  ot  0115  10  increase  tne  afifgu  01  tnc 

J         ?  '       "  * M-  9 jJ-    ^^^^ M^^nfSfl^M  A^M!  l^w^^vm*CvM 

arymgot  tne  pamt  Dotn  DyevaporaooiianciDy  onuixa- 
ikm;  and  finally,  to  act  as  a  Heading  a0ort  om  the  4 
the  pant  whiter;  this,  hipi.m,  is  not  so 


urtnin  their 


jipiuiluil  aliili  ilmii  mii 

letnn  distillales  with  which  the 

•ami  B 

* 


H  is  dedred,  Le.,  whether  of  Texas,  Ruffian,  or  of 
some  other  origin.  It  is  prepared  so  thai  it  has  a  flask 
point  rfgjitly  above  that  of  turpentine,  and  hence  as  a 


fire  rist  it  is  as  safe  as  iifi^pniMn&j  wiMen  is  in 

and  at  a  rate  about  or  slightly 
turpentine.    In  seeming  penetration  of  the  paint  it  is 
fuUy  equal  to  turpentine  and  is  free  front  objectionable 
•piliim    In  uulei  to  o  vis  come  the  drfi<  jmcy  off  not 
•••••••••g  the  paint  in  drying  by  oikiiation  and  tne 

lack  of  blesuAing  acdoa  on  the  Enseed  ofl,  several  paint 
pM^if^.ijMMM.  add  a  •••Bbiiiil  percentage  off  spirits  of 


turpentine  to 

153.  Reporting 
ahras  of  paints  should  be  very  careful  in 
composition  of  the  volatile  oik  used  in 


74  PAINT  AND  VARNISH  PRODUCTS. 

should  not  confound  these  turpentine  substitutes  with 
ordinary  benzine,  which  costs  considerably  less  than 
half  as  much  and  is  dangerous  to  use  on  account  of  the 
fire  risk  and  is  too  volatile  to  be  accepted  as  a  proper 
turpentine  substitute.  The  analysis  of  these  substitutes 
when  once  incorporated  into  the  paint  is  somewhat 
difficult,  but  with  care  may  be  obtained  by  distillation, 
as  above  mentioned.  Having  secured  the  volatile  dis- 
tillate and  having  freed  it  from  all  traces  of  water,  it 
may  be  redistilled,  using  a  small  distilling  flask  and 
carefully  noting  the  temperatures  at  which  the  product 
passes  over.  The  substitutes  of  recognized  merit  dis- 
till usually  between  150°  and  200°  C.  Any  benzine 
present  will  pass  over  below  150°  C.,  and  kerosene 
mostly  above  200°  C.  If  the  latter  is  present,  how- 
ever, a  large  portion  will  not  be  volatile  in  the  steam 
distillation  and  will  remain  in  the  linseed  oil,  being 
readily  detected  in  the  latter  by  pouring  six  drops  in  a 
few  cubic  centimeters  of  an  alcoholic  solution  of  potash, 
boiling  gently  for  two  minutes,  and  pouring  into  a  little 
distilled  water,  a  decided  cloudiness  indicating  the  pres- 
ence of  unsaponifiable  petroleum  oils. 

134.  Analyses.  The  following  data  clearly  indicate 
the  characteristics  of  the  petroleum  products  which  are 
now  being  offered  in  large  quantities  as  satisfactory 
in  whole  or  in  part  for  spirits  of  turpentine : 


TURPENTINE   SUBSTITUTES. 


75 


ANALYSIS   OF   DIAMOND   T   SPIRITS. 

Specific  Gravity,  0.8185  -  41.38°  Beaume. 
Flash  Test,  96°  F.   (open)  -  35.56°  C. 

DISTILLATION   BY   TEMPERATURES. 


C.  C. 

Commencing  at     . ...'.-„. ' '.    .    .    .    .  151.67 

From .    .    ,   ,    .    .  151. 67  to  157.23 

Do.    .    .    .    .    .    .    .   ......  157.23  to  162.78 

Do 162.78  to  168.34 

Do 168. 34  to  173. 89 

Do 173.89  to  179.45 

Do 179. 45  to  185. 00 

Do 185.00  to  190.56 

Do 190. 56  to  196.11 

Do. ,^.' V   .  196.11  to  201. 67 

Do 201. 67  to  207. 23 

Do 207.23  to  212.78 

Do .  212. 78  to  218. 34 

Do ,  \    .    .    .  218.34  to  223.89 

Do 223.89  to  229.45 

Do 229.45  to  235. 00 

Do 235.00  to  240. 56 

Do 240.56  to  246.11 

Do.  ...  246.11  to  248. 89 


10% 

•17% 

•28% 

•38% 

•47% 

56% 

65% 

•71% 

76% 

80% 

85% 

88% 

91% 

93% 

94% 

95% 

97% 


Name  of  Material. 

Texene. 

Turpentine. 

P.  Naphtha. 

Sulphur                                     

Per  cent. 
.008 

.000 
.022 
None 
None 

18.2 
18.4 
20.6 
39.8 
65.7 
76.7 
95.3 
99.4 
5  days 
Complete 

Per  cent. 
.003 
.002 
.510 

None 
None 

15.7 
12.1 
15.5 
33.6 
55.6 
91.6 
Comp. 
Comp. 
4  days 
5  in  all  pro 

Per  cent. 
.003 

.001 

.050 

None 
None 

19.8 
20.0 
74.5 
99.7 
Comp. 
Comp. 
Comp. 
Comp. 
1  day 
portions. 

Solubility  of  white  lead  in         .... 

Non-vol   solids  at  212°  F 

Discoloration  of  outside  paint  .... 
Discoloration  of  inside  paint  .      ... 
Amount   of  paint   vehicle    separated 
from  paint  after  six  days: 
In  outside  paint  
In  inside  paint                         .... 

Loss  in      3  hrs.  at  room  temp.     .    ... 
Do       24                do            

Do       48                do        

Do       72                do    .           .... 

Do       96                do        

Do      120                do 

Evaporation  completed  in  approx.    .    . 
Solubility  in  linseed  oil     .    .    .^.    .-. 

76 


PAINT  AND  VARNISH  PRODUCTS. 


DISTILLATION  FIGURES  OF  TEXENE,  TURPENTINE,  AND 
NAPHTHA. 


Texene. 

Turpentine. 

Naphtha. 

1st.       10% 
2d.         10% 

distilled  bet.  deg.  Fahr.  . 
Do  

300-307 
307-313 

307-315 
315-316 

169-208 
208-216 

3d.       105% 

Do  

313-322 

316-318 

216-221 

4th.     105% 

Do  

322-338 

318-318 

221-226 

5th        10% 

Do. 

338-351 

318-318 

226-235 

6th.       10% 

Do 

351-361 

318-318 

235-243 

7th        10% 

Do. 

361-372 

318-318 

243-252 

8th.       10% 

Do  

372-390 

318-320 

252-266 

9th.       10% 

Do  

390-417 

320-325 

266-291 

10th.       10% 

Do.  .    .-  

417-441 

325-338 

291-313 

135.  Distillation  with  steam  through  a  LeBel-Hennin- 
ger  column,  as  described  in  the  preceding  chapter,  with 
the  Sun  Oil  Company's  No.  18  Oil,  which  is  a  well- 
known  petroleum  substitute,  gave  the  following  results : 

PETROLEUM  SPIRITS. 

Flash  Point,  92°  F.     (Open).     Distillation,  145°  C.  -  225°  C. 
Time  Distillation,  P.S.,  74  m.     304  c.c. 


Comb.  Distil- 
late. 

Water. 

Petroleum 
Spirits. 

Temperature. 

Time. 

c.c. 

c.c. 

c.c. 

Deg.  C. 

m. 

1 

100 

42 

58 

95 

6 

2 

100 

50 

50 

96 

7 

3 

100 

58 

42 

97 

7 

4 

100 

64 

36 

98 

8 

5 

100 

71 

29 

98 

8 

6 

100 

77 

23 

98 

8 

7 

100 

81 

19 

98 

8 

8 

100 

84 

16 

98 

8 

9 

100 

88 

12 

98 

8 

10 

100 

89 

11 

98 

8 

Residue .8 


CHAPTER  X. 

THE  INERT  PIGMENTS. 

136.  Classification.     The  inert  pigments  comprise 

Barium  sulphate  (barytes,  blanc  fixe). 

Barium  carbonate. 

Calcium  carbonate   (whiting,  Paris  white,  white 

mineral  primer). 

Calcium  sulphate  (gypsum,  terra  alba). 
China  clay  (kaolin). 
Asbestine  (magnesium  silicate) . 
Silica  (silex). 

The  properties  of  the  various  active  pigments  have 
been  discussed  under  their  methods  of  manufacture  and 
need  not  be  taken  up  here. 

137.  Inert  pigments.    The  inert  pigments  have  widely 
different  properties,  not  only  from  a  chemical  stand- 
point but  from  a  physical  standpoint  as  well;  and  while 
two  pigments  may  have  the  same  chemical  composition, 
they  may  differ  greatly  in  physical  properties,  produc- 
ing  entirely   different   results   when   used   in   paints. 
Hence  it  is  practically  impossible  from  the  chemical 
analysis  to  judge  the  service  values  of  paints  containing 
inert  pigments.     Chemical  analysis,  however,  in  con- 
junction with  a  careful  microscopic  examination,  espe- 
cially if  a  polarizing  microscope  be  used,  may  give 
some  idea  of  what  the  service  value  should  be. 

138.  Barium  sulphate  (barytes,  blanc  fixe).     Barytes  is 
perhaps  the  most  extensively  used  of  the  inert  pigments. 
It  more  nearly  approximates  white  lead  in  specific  grav- 

77 


78  PAINT  AND  VARNISH  PRODUCTS. 

ity  and  oil-taking  capacity  than  any  of  the  others.  It 
is  absolutely  unaffected  by  acids,  alkalies,  or  atmos- 
pheric influences  of  any  kind.  Its  hiding  power  or 
opacity  when  ground  in  oil  is  very  low,  and  hence  when 
used  in  any  considerable  percentage  in  a  mixed  paint 
or  combination  lead  its  presence  is  indicated  by  the 
reduced  opacity  of  the  paint  film.  The  requisites 
of  a  high  grade  of  barytes  are  whiteness  and  fineness. 
Commercial  grades  often  contain  varying  percentages 
of  calcium  carbonate,  which  will  be  indicated  by  effer- 
vescence when  treated  with  hydrochloric  acid.  Occa- 
sionally a  considerable  percentage  of  calcium  sulphate 
may  be  found  which  may  be  readily  estimated  by 
extracting  with  boiling  water  and  determining  the 
calcium  in  the  filtrate. 

During  the  past  few  years  numerous  new  barytes 
deposits  have  been  opened  up  and  in  some  instances 
have  afforded  a  product  of  doubtful  value  to  the  paint 
manufacturer,  due  to  a  lack  of  proper  grinding  and  a 
peculiar  crystalline  structure  which  gives  much  trouble 
in  the  paint  mixer  and  grinding  mill  and  causes  excessive 
settling  in  the  package.  In  fact  it  is  always  advisable 
for  the  chemist  to  have  his  report  confirmed  by  trying 
out  the  product  in  question  in  one  or  more  regular 
formulas  in  the  factory.  Neither  is  the  color  maker 
immune  from  trouble  with  his  barytes,  especially  in  the 
manufacture  of  chrome  greens,  resulting  in  excessive 
settling  of  his  green  in  mixed  paints  and  manufacturing 
trades  paints,  especially  dipping  paints.  The  cheaper 
grades  of  barytes  have  a  yellowish  gray  color  and  are 
often  treated  with  sulphuric  acid  to  improve  the  color 
by  removing  the  iron.  A  considerable  portion  of  the 
barytes  on  the  market  is  " blued,'7  either  by  precipitat- 
ing as  Prussian  blue,  the  iron  sulphate  obtained  by 


THE  INERT  PIGMENTS.  79 

the  treatment  with  sulphuric  acid  or  by  adding  the 
Prussian  or  ultramarine  blue  separately.  The  major- 
ity of  paint  manufacturers,  however,  prefer  to  blue 
their  goods  themselves,  if  necessary,  during  the  pro- 
cess of  manufacture.  The  fineness  with  which  barytes 
has  been  ground  can  easily  be  determined  by  examina- 
tion under  the  microscope  after  the  acid  soluble  pig- 
ments have  been  dissolved  out. 

139.  Free  acid.    Each  shipment  of  barytes  should  be 
carefully  examined  for  free  acid,  which  can  be  easily 
done  by  placing  a  sample  on  a  strip  of  litmus  paper  in 
a  watch  glass  and  moistening  with  a  little  distilled 
water.     The  degree  of  reddening  will  indicate  whether 
more  than  a  minute  trace  of  free  acid  is  present.     In 
case  of  doubt,  a  quantitative  determination  should  be 
made.     The  presence  of  free  sulphuric  acid,  especially 
in  the  case  of  a  combination  lead  ground  in  a  warm 
mill,  will  cause  a  decided  hardening  in  the  keg.     Also 
if  an  acid  barytes  be  ground  with  lithopone  the  offen- 
sive odor  of  hydrogen  sulphide  will  be  very  apparent, 
not  only  in  the  grinding  room  but  when  the  package 
is  subsequently  opened. 

140.  Blanc  fixe.     This  pigment  is  a  precipitated  barium 
sulphate.     Owing  to  its  more  amorphous  character  it 
has  a  much  greater  hiding  power  than  barytes.     Its 
oil-taking  capacity  is  greater;  it  does  not  settle  in  a 
paint  so  badly  as  barytes  and  is  much  whiter;  its  cost, 
however,  is  about  twice  as  great.     It  is  largely  used  as 
an  inert  base  for  organic  lakes. 

141.  Barium  carbonate.     This  pigment  is  used  compar- 
atively little  in  the  United  States  as  a  paint  pigment. 
In  physical  and  chemical  properties  it  much  resembles 
white  mineral  primer,  a  form  of  calcium  carbonate, 
although  it  does  not  require  so  much  oil  in  grinding. 


80  PAINT  AND  VARNISH  PRODUCTS. 

Its  specific  gravity  is  about  that  of  barytes.  It  dis- 
solves readily  in  acetic,  nitric,  and  hydrochloric  acids; 
sulphuric  acid  converts  it  slowly  into  insoluble  barium 
sulphate.  In  the  hundreds  of  mixed  paints  examined 
by  the  writer  barium  carbonate  was  found  to  be  present 
in  only  one  paint,  although  its  presence  in  certain 
organic  lakes,  especially  in  certain  shades  of  red,  is  not 
uncommon  in  a  precipitated  form. 

142.  Calcium  carbonate,  Paris  white,  whiting,  alba  whit- 
ing, white  mineral  primer. 

Under  the  heading  of  calcium  carbonate  we  have 
three  distinct  classes  of  pigments,  —  those  obtained 
from 

(1)  English  cliffstone  or  similar  chalk  formations, 
such  as  Paris  white,  gilders'  whiting,  and  commercial 
whiting. 

(2)  Marble  or  a  crystalline  calcium  carbonate,  such 
as  marble  dust,  white  mineral  primer,  etc. 

(3)  Precipitated   calcium   carbonate,    such   as   alba 
whiting. 

The  English  cliffstone  pigments  are  usually  put  on 
the  market  in  about  three  grades.  The  first  grade  is 
the  whitest  and  most  finely  ground  and  bolted  and  is 
usually  sold  under  some  such  name  as  Paris  white,  and 
finds  its  use  largely  in  first- quality  mixed  paints  and 
combination  leads.  The  second  grade  is  coarser 
and  has  a  slightly  grayish  tint  and  is  usually  sold 
under  some  such  name  as  gilders'  whiting.  It  is  also 
bolted,  and  is  used  in  second  and  third  grade  paints. 
The  third  grade  is  inferior  in  color  and  fineness  to  the 
other  two  grades.  It  finds  its  chief  use  in  kalso- 
mine;  although  it  is  used  in  some  of  the  very  inferior 
paints,  it  never  should  be,  owing  to  the  fact  that  it 


THE   INERT   PIGMENTS.  81 

is  not  bolted,  and  therefore  contains  some  relatively 
large  particles.  It  is  usually  sold  as  commercial 
whiting. 

143.  White  mineral  primer.  The  various  forms  of 
white  mineral  primer  are  of  an  entirely  different  nature 
physically  from  the  cliffstone  products,  being  fragments 
of  small  crystals.  They  have  very  little  body  in  oil, 
being  nearly  transparent.  They  are  usually  whiter 
than  Paris  white  and  possess  much  greater  tooth,  but 
are  not  much  used  in  mixed  paints  owing  to  the  fact 
that  they  settle  badly  in  the  can  and  have  very  little 
opacity.  They  find  their  chief  use  in  primers  and  in 
putty  for  making  it  work  shorter.  Being  of  a  crystal- 
line nature  it  is  natural  that  they  require  less  oil  in 
grinding  than  Paris  white. 

Alba  whiting  and  other  precipitated  calcium  car- 
bonate pigments  are  very  white,  but  being  very  light 
and  fluffy  require  an  enormous  amount  of  oil  in 
grinding. 

While  it  is  not  an  easy  matter  to  distinguish  these 
different  products  in  a  paint,  yet  the  microscope  is  of 
much  value  in  determining  the  fineness  of  grinding. 

The  paint  chemist  is  frequently  required  to  pass  on 
samples  of  Paris  white,  which  appear  much  whiter 
than  his  standard  samples.  On  close  examination  these 
will  usually  be  found  to  possess  a  semicrystalline  nature, 
therefore  are  deficient  in  opacity,  and  are  not  true 
Paris  whites. 


82  PAINT  AND  VARNISH  PRODUCTS. 


Quantitative  Analysis  of  the  Calcium  Carbonate 
Pigment. 

144.  Moisture.    Heat  2  grams  at  105°  C.  for  two  hours, 
cool,  and  weigh. 

145.  Silica.    Weigh  one-half  gram  into  a  suitable  sized 
casserole.     Cover,  add  5  c.c.  of  hydrochloric  acid  (sp. 
gr.  1.1)  by  means  of  a  pipette,  without  raising  the  cover. 
After  the  effervescence  has  ceased,  rinse  off  the  beaker 
cover  with  a  little  hot  water.     Evaporate  to  dryness 
and   cool.     Add   2   c.c.   of  concentrated  hydrochloric 
acid,  again  evaporate,  and  heat  gently  for  a  few  min- 
utes.     Cool  and  dissolve  in  100  c.c.  of  hot  water  and 
10  c.c.  of  strong  hydrochloric  acid,  filter,  wash,  ignite, 
and  weigh.     If  1  per  cent  or  under,  it  may  be  regarded 
as  silica.     If  more,  it  should  be  fused  with  sodium  car- 
bonate, dissolved  in  water  and  hydrochloric  acid,  in 
the  same  casserole,  and  evaporated  to  dryness.     Heat 
gently.     Add  a  little  more  hydrochloric  acid  and  de- 
hydrate again.     Finally  take  up  in  water  acidulated 
with  hydrochloric  acid,  filter,  ignite,  and  weigh  as  silica. 
The  filtrate  from  the  silica  fusion  is  treated  as  described 
under  149. 

146.  Alumina  and  iron.    The  filtrate  from  the  original 
residue  is  made  just  perceptibly  alkaline  with  dilute 
ammonia,  the  iron  and  alumina  filtered  off,  ignited,  and 
weighed  in  the  usual  manner. 

147.  Calcium.     The  filtrate  from  the  iron  and  alumina 
is  made  acid  with  acetic  acid,  boiled,  and  40  c.c.  to  50  c.c. 
of  ammonium  oxalate  solution  added.     Continue  boil- 
ing for  5  minutes,  filter,  and  wash  thoroughly.     Return 
filter  and  precipitate  to  same  beaker.     Add  200  c.c.  of 
boiling  water  and  25  c.c.  of  dilute  sulphuric  acid  and 


THE  INERT  PIGMENTS.  83 

titrate  with  standard  tenth-normal  potassium  perman- 
ganate. 

1  c.c.  tenth-normal  permanganate  =  0.0028  g.  CaO 

1  c.c.  tenth-normal  permanganate  =  0.0050  g.  CaCOs 

1  c.c.  tenth-normal  permanganate  =  0.0086  g.  CaSO4 .  2  H2O 

1  c.c.  tenth-normal  permanganate  =  0.0068  g.  CaSC>4 

1  c.c.  tenth-normal  oxalic  acid        =  0.0028  CaO 

Cryst.  oxalic  acid  X  0.444  =  CaO 

EXAMPLE:  Wt.  sample  taken          =  0.250  g. 

Titration  with  permanganate          =  50.5  c.c. 

25  c.c.  standard  iron  solution          =31.8  c.c.  permanganate 

1  c.c.  standard  iron  solution  =  .007  g.  iron 

1  c.c.  tenth-normal  iron  solution     =  .0056  g.  iron 

25  c.c.  standard  iron  solution  =  31.25  c.c.  tenth-normal  per- 
manganate. 

1  c.c.  permanganate  solution  used  =  0.983  c.c.  tenth-normal  per- 
manganate. 

50.5  c.c.  X  0.983  =  4964  c.c. 

(49.64  c.c.  X  0.0050)  ^  0.250          =  99.28%  CaCO3. 

148.  Magnesium.     The  filtrate  from  the  calcium  oxa- 
late  is  cooled  and  treated  with  hydrogen  sodium  phos- 
phate, allowed  to  stand  for  one-half  hour,  then  25  c.c. 
of  strong  ammonia  added,  allowed  to  stand  one  hour,  fil- 
tered on  a  Gooch  crucible,  ignited,  and  weighed. 

Wt.  precipitate  =  0.7575  =  Wt,  Magnesium  car- 
bonate. 

149.  Calcium  and  magnesium  oxides.     The  filtrate  from 
the  silica  fusion  should  be  treated  separately  from  the 
main  filtrate,  as  the  calcium  and  magnesium  obtained 
from  it  are  to  be  reported  as  oxides  and  not  as  carbon- 
ates.    Precipitate  the  iron  and  alumina,  calcium  and 
magnesium,  as  described  under  146,  147,  and  148. 

NOTE.  —  If  the  sample  contains  considerable  magnesium  carbonate, 
the  following  modification  should  be  observed.  After  filtering  off  the 
iron  and  aluminium  hydroxides,  they  are  redissolved  in  another  beaker, 
diluted,  and  again  precipitated  and  filtered  into  the  main  filtrate.  The 


84  PAINT  AND  VARNISH  PRODUCTS. 

same  treatment  is  given  to  the  calcium  oxalate.  Magnesium  com- 
pounds when  present  in  considerable  percentages  badly  contaminate  the 
other  precipitates. 

150.  ANALYSES  OF  CALCIUM  AND  MAGNESIUM  CARBON- 
ATE PIGMENTS  BY  AUTHOR. 


Moisture 

I. 

White 
Ocher. 

0.11 

II. 

Whiting. 

0.30 

III. 

English 
Cliff  stone. 

1.60 

IV. 

Magne- 
site. 

0.07 

Silica 

1  21 

0  90 

2  02 

2.04 

Iron  oxide  and  alumina.  .  . 
Calcium  carbonate  .... 
Magnesium  carbonate  .  .  . 

.63 
97.39 
0.56 

0.20 
96.55 
1.84 

1.00 
92.81 
2.52 

3.01 
10.84 
83.91 

Undetermined 0.10          0.21          0.05          0.13 

100.00       100.00       100.00       100.00 

151.  Calcium  sulphate  (gypsum,  terra  alba).     This  pig- 
ment is  found  in  combination  white  leads  and  exterior 
white  paints  only  to  a  limited  extent.     Its  chief  use 
seems  to  be  in  certain  lines  of  railroad  paints  and  in 
dipping  or  implement  paints.     It  is  also  used  to  some 
extent  as  a  base  upon  which  to  strike  certain  organic 
lakes,  notably  the  para  reds.     The  writer,  despite  the 
favorable  opinions  of  many  eminent  paint  authorities, 
does  not  believe  that  calcium  sulphate,  or  gypsum,  as 
it  is  more  commonly  known,  is  adapted  for  use  in 
exterior  paints  owing  to  its  solubility  in  water,  it  being 
soluble  about  one  part  in  five  hundred.     A  linseed  oil 
paint  film  is  by  no  means  impervious  to  moisture,  and 
the  continued  action  of  rains  and  storms  cannot  be 
otherwise  than  favorable,  as  the  solvent  action  of  the 
water  in  removing  a  portion  of  the  gypsum  renders  the 
paint  film  more  porous   and  its   disintegration  more 
rapid. 

152.  Calcium  sulphate  in  oxide  of  iron  pigments.     Ve- 
netian reds  often  contain  50  to  80  per  cent  of  cal- 
cium sulphate.     The  better  class  of  Venetian  reds  are 


THE  INERT  PIGMENTS.  85 

composed  of  50  per  cent  of  ferric  oxide  and  50  per  cent 
of  calcium  sulphate.  This  calcium  sulphate  should 
not  be  confounded  with  the  forms  above  discussed, 
as  it  has  been  subjected  to  the  action  of  a  high  heat 
and  is  therefore  insoluble  in  water,  and  is  regarded  as 
a  proper  constituent  of  Venetian  reds. 

153.  Analysis  of  agalite,  terra  alba,  etc.  These  pig- 
ments have  essentially  the  same  composition  —  calcium 
sulphate  plus  2  molecules  of  water.  The  same  method 
of  analysis  may  be  pursued  as  described  under  the 
analysis  of  calcium  carbonate  pigments.  In  addition, 
it  is  necessary  to  determine  the  combined  water  by 
ignition  to  constant  weight,  and  also  to  determine  the 
combined  sulphuric  acid,  which  may  be  done  as  fol- 
lows: 

Boil  0.5  gram  of  the  pigment  in  30  c.c.  of  strong 
hydrochloric  acid  for  10  minutes  in  a  covered  beaker. 
Dilute  with  250  c.c.  of  boiling  water,  boil  5  minutes, 
filter,  make  filtrate  neutral  with  ammonia,  then  dis- 
tinctly acid  with  hydrochloric  acid,  and  bring  to  boiling. 
Add  25  c.c.  of  barium  chloride,  boil  10  minutes,  filter, 
wash  with  hot  water,  ignite,  and  weigh. 

Wt.  barium  sulphate  X  0.3433  =  combined  sulphuric 
acid. 


154.  ANALYSES  OF  CALCIUM  SULPHATE  PIGMENTS  BY 

AUTHOR. 

I.  II. 

Agalite.  Terra  Alba. 

Moisture  and  combined  water    ...       19.02  20.67 

Iron  oxide  and  alumina 0.29  0.67 

Silica       5.60  0.70 

Calcium  sulphate      74.90  76.52 

Magnesium  sulphate 1 . 36 

Undetermined 0.19  .08 


100.00  100.00 


86  PAINT  AND  VARNISH  PRODUCTS. 

155.  Aluminum  silicate    (China  clay,  kaolin,  tolanite). 
This  pigment  also  finds  but  little  use  in  combination 
white  leads,  owing  to  its  low  specific  gravity.     It  is, 
however,  used  extensively  in  mixed  paints,  implement 
paints,  and  as  an  inert  base  upon  which  to  strike  para 
and  other  organic  reds,  especially  for  colors  which  are 
used  in  dipping  paints.     Its  functions  and  properties 
are  very  similar  to  those  of  magnesium  silicate,  it  being 
essentially  a  suspender  for  preventing  settling  in  paints. 
It  is  very  inert  in  its  action  with  acids  and  alkalies. 
Strong  hydrochloric  acid  with  continued  boiling  will 
dissolve  a  very  slight  fraction  of  1  per  cent,  hence 
traces  of  aluminum  may  be  found  in  a  hydrochloric 
acid  solution  of  a  paint  containing  aluminum  silicate. 
Some  of  the  silicates  much  in  favor  with  the  paint  trade 
contain  a  considerable  percentage  of  what  is  apparently 
uncombined  silica.     In  mixed  paint  it  is  often  used 
with  magnesium  silicate.     Hence  a  microscopic  exam- 
ination is  usually  required  to  determine  whether  the 
latter  is  present  or  not.     It  yields  to  treatment  by 
fusion  with  sodium  carbonate  more  readily  than  mag- 
nesium silicate.     When  subjected  to  a  high  tempera- 
ture it  loses  11  to  13  per  cent  of  water  of  hydration. 

156.  Magnesium     silicate     (asbestine     pulp,     talcose). 
This  pigment  is  sold  under  the  various  names  of  white 
silicate,  asbestine,  asbestine  pulp,  etc.     Large  amounts 
are   obtained    from  natural    deposits  in  and    around 
Gouverneur,  N.  Y.     It  has  a  very  low  specific  gravity, 
and  is  much  used  in  lead  and  zinc  paints  to  prevent 
those  pigments  from  settling  hard  in  the  bottom  of  the 
package.     Chemically  it  is  very  inert,  being  unacted 
upon  by  any  of  the  ordinary  acids.     It  is,  however, 
decomposable  with  hydrofluoric  acid  in  a  platinum  dish 


THE  INERT   PIGMENTS.  87 

and  by  fusion  with  sodium  carbonate.  Fusion  with 
potassium  bisulphate  decomposes  it  only  partially. 
Continued  heating  at  a  bright  red  heat  will  cause  a 
loss  of  3  to  5  per  cent  in  weight,  due  to  loss  of  water 
of  hydration.  It  is  easily  recognized  under  the  micro- 
scope by  the  fibrous  or  rod-like  structure  of  the 
particles. 

157.  Silica  (silex).    There   are  two  distinct  kinds  of 
silica  to  be  found  on  the  market,  —  that  obtained  from 
crushed  quartz,  which  is  a  very  pure  form  of  silica,  and 
an  impure  form  found  in  natural  deposits,  especially  in 
Illinois.     The    former    possesses    a    very    pronounced 
" tooth,"  under  the  microscope  the  particles  are  very 
sharp  and  jagged,  and  it  is  quite  transparent  in  oil. 
The  second  form  is  composed  of  rounded  particles  of  a 
complex  chemical  nature;  besides  free  silica  there  are 
usually  found  associated  with  it  calcium  carbonate, 
aluminum  silicate,  and  magnesium  silicate,  besides  a 
small  amount  of  magnesium  carbonate.     This  product 
requires  more  oil  in  grinding,  and  has  much  more  body, 
but  considerably  less  tooth. 

158.  Fusion  with  sodium  carbonate.     One-half  gram  is 
thoroughly  mixed  with  10  grams  sodium  carbonate  and 
one-half  gram  potassium  nitrate  placed  in  a  covered 
platinum  crucible  and  fused  until  quite  clear  and  quiet. 
Cool,  and  dissolve  in  water  in  a  casserole,  provided  with 
beaker  cover,  on  the  hot  plate.     Make  acid  with  hydro- 
chloric acid,  adding  the  acid  with  a  pipette,  keeping 
the  casserole  covered  to  avoid  loss.     Also  rinse  out  the 
crucible  with  a  little  acid.     After  the  effervescence  is 
over,  wash  off  the  watch  glass,  and  evaporate  to  dryness 
on  the  sand  bath.     Cool,  moisten  residue  with  hydro- 
chloric acid,  and  evaporate  to  complete  dryness  again. 
Dissolve  in  10  c.c.  of  hot  water  and  10  c.c.  of  hydro- 


88  PAINT  AND  VARNISH  PRODUCTS. 

chloric  acid.  Filter,  ignite,  and  weigh  precipitate  as 
silica. 

If  barytes  is  suspected  to  be  present,  the  sodium  car- 
bonate fusion  is  dissolved  in  hot  water  and  the  barium 
carbonate  filtered  off,  dissolved  in  hydrochloric  acid,  and 
precipitated  with  a  few  drops  of  sulphuric  acid  in  the 
usual  manner.  The  filtrate  from  the  barium  sulphate 
is  added  cautiously  to  the  filtrate  from  the  barium 
carbonate,  the  mixed  filtrate  made  acid,  and  the  silica 
dehydrated  as  described  above. 

159.  The  filtrate  from  the  silica  is  made  slightly  alka- 
line with  ammonia  and  the  iron  and  alumina  precipi- 
tated, washed,  redissolved,  reprecipitated  to  free  from 
sodium  salts,  filtered,  ignited,  and  weighed  in  the  usual 
manner. 

The  filtrate  from  the  iron  and  alumina  is  treated  with 
ammonium  oxalate  and  after  allowing  to  stand  in  a 
warm  place  the  calcium  is  filtered  off,  ignited,  and 
weighed  as  calcium  oxide.  If  desired  the  calcium 
may  be  estimated  volumetrically,  as  described  under 
the  analysis  of  white  mineral  primers,  etc. 

The  filtrate  from  the  calcium  is  tested  for  magnesium 
with  sodium  hydrogen  phosphate,  and  if  found,  esti- 
mated in  the  usual  manner. 

The  carbon  dioxide  is  determined  in  a  separate  por- 
tion of  the  sample.  The  amount  found  is  combined 
with  the  requisite  amount  of  calcium  to  form  calcium 
carbonate.  Any  excess  of  calcium  is  reported  as  the 
oxide,  it  being  in  combination  with  the  silica.  The 
magnesium  is  usually  calculated  as  magnesium  oxide, 
unless  the  carbon  dioxide  is  in  excess  of  the  calcium 
present,  in  which  case  it  is  calculated  to  magnesium 
carbonate  and  the  remainder  of  the  magnesium  to  the 
oxide. 


THE  INERT   PIGMENTS.  89 

160.  Moisture.     Heat  2  grams  at  105°  C.  for  3  hours, 
cool,  and  weigh. 

161.  Combined  water.     Weigh  2  grams  into  a  platinum 
crucible,  heat  in  the  muffle  or  over  a  strong  Bunsen  flame 
for  1  hour.     Loss  in  weight  equals  combined  water  un- 
less an  appreciable  amount  of  carbonate  is  present. 

162.  Determination  of  the  alkali  metals,  sodium  and 
potassium.      Heat  gently  1  gram  of  the  sample  inti- 
mately mixed  with  1  part  ammonium  chloride  to  8  parts 
of  pure  calcium  carbonate.     The  alkalies  as  well  as 
some  of  the  calcium  are  converted  into  chlorides.     Cool, 
treat  with  water.     The  alkali  chlorides  will  dissolve, 
while  most  of  the  calcium  remains  undissolved.     Filter, 
precipitate  the  calcium  with  ammonia  and  ammonium 
carbonate,  filter,  evaporate  to  small  bulk,  and  precipi- 
tate any  remaining  calcium.     Filter.     The  solution  now 
contains  as  fixed  compounds  only  sodium  and  potas- 
sium  chlorides.     Evaporate   nearly   to    dryness   in   a 
weighed  platinum  dish  on  water  bath.     Cover  and  dry 
completely  on  the  hot  plate,  exercising  great  care  to 
prevent  the  spattering  of  the  material.     Finally  heat 
gently  with  a  Bunsen  burner,  which  must  be  held  in  the 
hand  and  the  flame  waved  under  the  dish  and  removed 
as  soon  as  any  portion  of  the  dish  becomes  red  hot. 
Cool  and  weigh.     Take  up  in  water  and  add  an  excess 
of  platino-chloride  solution.     Evaporate  to  a  sirupy  con- 
sistency, take  up  with  80  per  cent  alcohol,  filter  through 
a  weighed  Gooch  crucible,  and  wash  with  alcohol.     Dry 
in  the  steam  oven. 

Wt.  of  precipitate  X  0.1941  =  wt.  Potassium  oxide. 

Calculate  to  potassium  chloride,  subtract  from  the 
weight  of  the  mixed  chlorides,  thus  obtaining  the  weight 
of  sodium  chloride,  which  may  then  be  calculated  to 
sodium  oxide. 


90 


PAINT  AND  VARNISH  PRODUCTS. 


163.  ANALYSES  OF  SILICAS  BY  AUTHOR. 

I.              II.  III. 

Moisture 0.21          0.06  0.43 

Ferric  oxide  and  alumina    ...         0.28          0.01  1.48 

Silica 99.40        99.88  53.48 

Calcium  carbonate 26 . 12 

Magnesium  carbonate      18. 17 

Undetermined 0.11          0.05  0.32 

100.00       100.00       100.00 

ANALYSES  OF   MAGNESIUM   SILICATES  BY  AUTHOR. 

I.  n. 

Moisture 0.50  0.29 

Combined  water 2 . 99  3 . 44 

Silica 58.60  56.76 

Ferric  oxide 0 . 09  0 . 18 

Alumina 1.43  2.84 

Calcium  carbonate 2 . 77 

Calcium  oxide 5 . 63  

Magnesium  oxide 30 . 45  33 . 50 

Undetermined 0.31  0.22 

100.00       100.00 

ANALYSES  OF  TOLANITE  BY  AUTHOR. 

Moisture 0 . 22 

Combined  water   . 10.42 

Ferric  oxide 0.09 

Alumina  sol.  in  HC1 0 . 39 

Silica 65.51 

Alumina 23.12 

Undetermined 0.25 

100.00 

TYPICAL  ANALYSES  OF  CLAYS.1 

I.              n.             in.  IV. 

Silica 45.45        66.20        72.66  64.84 

Alumina 38.75        24.11         17.33  24.31 

Ferric  oxide 1.15          0.79           1.05  1.60 

Calcium  oxide 0. 13  0. 11 

Magnesium  oxide 0.11        

Potassium  oxide 0 . 17          0 . 96          0 . 36  0 . 24 

Sodium  oxide 0 . 38  0 . 32 

Combined  water,  etc 13.05          7.20          8.09  8.58 

Undetermined 1.32          0.74 


100.00      100.00      100.00 
1  Geological  Survey  of  North  Dakota,  1901. 


100.00 


THE   INERT  PIGMENTS.  91 

164.  Specifications  for  paste  wood  filler.  ("Bureau  of 
Supplies  and  Accounts,  Navy  Department,"  1902.) 
Paste  wood  filler  shall  contain  the  following: 

Per  cent. 

Silicate 65 

Raw  linseed  oil      10 

Best  quality  rubbing  varnish 25 

The  silicate  must  be  dry,  finely  ground,  and  when 
subjected  to  microscopic  test  the  particles  must  show  a 
needle-pointed  shape.  Powdered  silicate  which  shows 
spherical  fragments  will  not  be  accepted. 

The  raw  linseed  oil  must  be  absolutely  pure,  well- 
settled  oil,  of  the  best  quality;  must  be  perfectly  clear, 
and  not  show  a  loss  of  over  2  per  cent  when  heated  to 
212°  F.  or  show  any  deposit  of  foots  after  being  heated 
to  that  temperature.  The  specific  gravity  must  be 
between  0.932  and  0.957  at  60°  F. 

The  rubbing  varnish  to  be  of  the  best  quality  and 
to  be  equal  in  quality  to  the  standards  of  rubbing  var- 
nish, which  can  be  seen  on  application  to  the  general 
storekeeper's  office  at  the  various  navy  yards.  Any  indi- 
cation of  the  use  of  rosin  or  any  other  adulterant  in  this 
varnish  will  be  sufficient  for  its  rejection. 

The  paste  wood  filler  when  thinned  with  turpentine 
to  a  brushing  consistency  must  dry  hard  on  glass  in  24 
hours.  It  must  not  rub  up  by  friction  under  the  finger, 
and  when  immersed  in  water  must  remain  intact  for  at 
least  4  hours.  It  must  dry  full  without  luster,  and 
be  transparent,  so  that  it  will  not  color  or  cloud  the 
work,  and  be  hard  enough  to  stand  sandpaper  without 
clogging  the  paper  after  12  hours. 


CHAPTER  XI. 

ANALYSIS   OF  WHITE  LEAD. 

165.  Color.     The  two  samples  are  weighed  out  in  gram 
lots  on  a  large  glass  plate,  twelve  drops  of  bleached 
linseed  oil  added  to  each  and  rubbed  up  thoroughly,  and 
matched  up  on  a  microscope  slide,   the  color  being 
judged  from  both  sides  of  the  glass.     After  comparing 
the  color,  place  the  slide  in  the  steam  oven  for  two 
hours.     This  will  give  some  idea  as  to  the  amount  of 
yellowing  that  will  occur  when  the  lead  is  used  in  paint- 
ing.    This  defect  is  particularly  marked  in  pulp  leads. 

1 66.  Opacity.     Two  grams  each  of  the  sample  and 
standard  are  very  carefully  rubbed  up  with  .01  gram 
of  ultramarine  blue  and  twenty-four  drops  of  oil  as 
described  under  the  section  on  the  "  Determination  of 
the  tinting  strength  of  colors."     The  more  strongly  the 
lead  is  colored,  the  weaker  it  is  in  hiding  power  or  opac- 
ity.    Adding  weighed  amounts  of  lead  until  the  colors 
are  of  equal  depth  will  show  the  ratio  between  the  two. 

167.  Painting  test.     The  painting  value  is  best  judged 
by  painting  test  boards,  as  described  under  the  section 
on  the  "  Comparison  of  paints  for  covering  power,"  and 
afterwards  exposing  them  under  suitable  conditions. 

1 68.  Sulphur  dioxide.     In  the  manufacture  of  quick- 
process  white  leads,  where  the  carbon  dioxide  is  obtained 
from  fuel  gases,  it  is  liable  to  contain  sulphur  compounds 
which  will  remain  in  the  white  lead  combined  in  the 
form  of  sulphite  of  lead. 

169.  The  sulphur  dioxide  may  be  estimated  by  treat- 
ing 10  grams  of  the  pigment  with  50  c.c.  of  water  and 

92 


ANALYSIS  OF  WHITE  LEAD.  93 

25  c.c.  of  hydrochloric  acid.  Allow  to  stand  5  minutes 
and  titrate  with  a  hundredth  normal  iodine  solution  as 
described  under  the  estimation  of  sulphur  dioxide  in 
zinc  pigments.  The  same  objections  apply  to  its  pres- 
ence in  white  lead  as  in  zinc  oxides. 

170.  Sandy  lead.1  "A.  certain  degree  of  density  is 
always  desired  in  white  lead,  since  both  the  corroder 
and  the  grinder  know  that  the  smaller  the  amount  of  oil 
required  to  bring  a  given  lead  to  paste  form,  the  cheaper 
it  is  for  him,  since  the  average  price  per  pound  of  lin- 
seed oil  is  greater  than  that  of  dry  lead,  while  the  same 
pigment  is  equally  sought  after  by  the  consumer,  since 
he,  too,  desires  density  and  opacity  in  this  pigment. 
However,  efforts  in  this  direction  are  not  infrequently 
carried  too  far,  with  the  result  of  a  crystalline  over- 
corroded  lead  which  settles  and  hardens  badly.  Such 
lead  causes  loss  and  trouble  both  to  the  grinder  and  the 


consumer." 


171.  Determination.  "  Based  upon  the  undesirable  fea- 
ture of  settling,  a  comparative  separation  is  easily  made. 
A  fairly  large  sample,  say  100  grams,  is  taken.  This,  if 
in  paste  form,  is  thinned  with  benzine  and  run  through 
a  fine  bolting  cloth.  Any  paint  skins  are  retained,  but 
all  of  the  lead  should,  when  sufficiently  thinned,  wash 
through  a  fine  bolting  cloth.  The  very  thin  paint  is 
now  thoroughly  stirred  and  allowed  to  settle  for  only  a 
short  time.  Nearly  all  of  the  benzine  is  now  poured  off 
and  then  the  washing  of  the  sediment  with  benzine  is  re- 
peated until  the  benzine  comes  off  nearly  clear,  leaving 
the  'sand'  alone  as  a  residue."  While  present  in  all 
commercial  lead,  the  amount  should  be  small,  scarcely 
exceeding  2.5  per  cent;  objectionable  samples  will  fre- 
quently show  much  more,  at  times  over  10  per  cent. 
1  Hooker,  Treatise  on  White  Lead,  page  24. 


94  PAINT  AND  VARNISH  PRODUCTS. 

172.  Tanbark.     The  determination  of  tanbark  and 
other  organic  matter  is  seldom  required.     It  may,  how- 
ever, be  made  by  dissolving  50  grams  of  the  sample  in 
75  c.c.  of  nitric  acid  diluted  with  250  c.c.  of  water. 
Filter  through  .a  weighed  Gooch  crucible,  provided  with 
a  disk  of  filter  paper  on  the  top  of  the  asbestos  felt, 
wash  thoroughly,  dry,  and  weigh.     The  amount  present 
should  not  exceed  one-tenth  of  one  per  cent,  according 
to  Hooker. 

173.  Sulphate  of  lead,  which  may  be  present  in  some 
of  the  quick-process  leads,  would  largely  remain  undis- 
solved  in  the  nitric  acid  solution  and  unless  removed 
would  be  weighed  up  as  tanbark,  etc.     When  present 
it  may  be  dissolved  by  placing  the  Gooch  crucible  and 
contents  in  a  small  beaker  containing  acid  ammonium 
acetate  for  a  few  minutes,  after  which  the  crucible  is 
placed  in  the  holder,  washed  with  a  further  quantity  of 
acetate  solution,  then  with  a  little  warm  water,  and 
dried  as  before. 

174.  Metallic  lead.    Like  the  determination  of  sandy 
lead  it  is  seldom  made.    Occasionally  in  poorly  prepared 
white  leads  a  sufficient  amount  may  be  present  to  war- 
rant a  determination,  in  which  case  it  is  best  made  in 
conjunction  with  the  determination  of  " sandy  lead," 
which,  after  being  weighed  up,  is  carefully  dissolved  in 
dilute  nitric  acid,  the  operation  being  checked  the  mo- 
ment the  sandy  white  lead  has  dissolved  by  dilution 
with  a  large  quantity  of  water.     The  particles  of  metal- 
lic lead  are  but  very  slightly  acted  upon  by  acid  and 
may  be  filtered  off  on  a  weighed  Gooch  crucible,  washed 
thoroughly,  dried,  and  weighed.     The  amount  found 
should  not  exceed  one-tenth  of  1  per  cent. 

175.  Lead  sulphate.     This  impurity  may  be  present  in 
small  quantities  in  white  leads  prepared  by  the  newer 


ANALYSIS  OF  WHITE  LEAD.  95 

processes  and  sometimes  in  old  Dutch  process  lead  in 
the  settling  tanks  and  wash-water  tanks.  When  present 
in  quantities  less  than  one-half  of  1  per  cent  it  should 
not  be  considered  as  seriously  objectionable. 

176.  Determination.     Dissolve  1  gram  in  water  25  c.c., 
ammonia   10  c.c.,  hydrochloric  acid  in  slight  excess. 
Dilute  to  200  c.c.,  and  add  a  piece  of  aluminum  foil 
which  should  about  cover  the  bottom  of  the  beaker. 
It  is  important  that  this  be  held  at  the  bottom  by  a 
glass  rod.     Boil  gently  until  the  lead  is  precipitated. 
Completion  of  this  is  shown  by  the  lead  ceasing  to  coat 
or  cling  to  the  aluminum.     Decant  through  a  filter, 
pressing  the  lead  sponge  into  a  cake  to  free  it  from  solu- 
tion.    Add  to  nitrate  a  little  sulphur-free  bromine  water, 
boil  until  the  bromine  is  expelled,  add  15  c.c.  of  barium 
chloride,  boil  10  minutes,  filter,  wash  with  hot  water, 
ignite,  and  weigh  as  barium  sulphate.    Calculate  to  lead 
sulphate  by  multiplying  by  1.3  as  a  factor. 

177.  Volumetric  estimation  of  lead,  Method  I.1      Dis- 
solve 1  gram  in  15  c.c.  nitric  acid,  specific  gravity  1.20, 
neutralize  the  solution  with  ammonia  in  excess,  and 
then  make  strongly  acid  with  acetic  acid.     It  is  then 
boiled  and  standard  potassium  bichromate  solution  is 
run  in  from  a  burette  in  sufficient  quantity  to  precipi- 
tate nearly  all  the  lead.    The  liquid  is  boiled  until  the 
precipitate  becomes  orange  colored.     The  titration  is 
continued,  one-half  cubic  centimeter  or  so  at  a  time,  the 
solution  being  well  stirred  after  each  addition  of  bichro- 
mate until  the  reaction  is  almost  complete,  which  can 
be  observed  by  the  sudden  clearing  up  of  the  solution, 
the  lead  chromate  settling  promptly  to  the  bottom  of 
the  beaker;  this  will  usually  occur  within  1  c.c.  of  the 
end  of  the  reaction.     The  titration  is  then  finished,  the 

Wainwright,  J.  Am.  Chem.  Soc.,  Vol.  XIX,  page  389. 


96  PAINT  AND  VARNISH  PRODUCTS. 

end  point  being  indicated  by  the  use  of  silver  nitrate 
as  an  outside  indicator,  on  a  white  plate. 

The  solution  of  the  lead  salt  should  be  as  concen- 
trated as  possible  before  titration  and  decidedly  acid 
with  acetic  acid.  The  titration  should  be  performed  in 
a  solution  kept  at  all  times  as  near  the  boiling  point  as 
possible. 

178.  Potassium  bichromate  solution.     This  should  be 
of  such  strength  that  1  c.c.  equals  approximately  0.01 
gram  of  metallic   lead,   and   should   be   standardized 
against  a  weighed  amount  of  pure  metallic  lead  as  de- 
scribed above. 

179.  Silver  nitrate    solution.     Dissolve  2.5  grams   of 
silver  nitrate  in  100  c.c.  of  water. 

NOTE.  —  This  method  is  applicable  for  determination  of  lead  in  red 
lead,  the  solution  being  effected  with  nitric  acid,  boiling,  and  adding 
dilute  oxalic  acid  drop  by  drop  until  the  lead  oxide  formed  is  completly 
dissolved. 

180.  Volumetric  estimation  of  lead,  Method  II.1     Dis- 
solve 0.5  to  1  gram  of   the  pigment  in  acetic  acid  if 
white  lead;  if  lead  sulphide,  dissolve  in  nitric  acid,  dilute 
with  25  c.c.  cold  water,  add  strong  ammonia  until  just 
alkaline  to  litmus  paper,   then  make  distinctly  acid 
with  strong  acetic  acid. 

181.  Heat  to  boiling,  dilute  to  about  200  c.c.  with 
boiling  hot  water,  and  titrate  with  standard  ammonium 
molybdate  solution.     Reserve  about  10  c.c.  of  the  hot 
solution  in  a  small  beaker,  run  in  molybdate  solution 
into  the  large  beaker  from  a  burette,  with  constant  stir- 
ring, until  a  drop  placed  in  contact  with  a  drop  of  tannic 
acid  solution  on  a  white  plate  gives  a  brown  or  yellow 
tinge.     Add  the  10  c.c.  reserved  and  finish  the  titration 
carefully  at  the  rate  of  two  drops  addition  at  a  time. 

1  Alexander's  Method,  Ore  Analysis,  Low,  page  113. 


ANALYSIS  OF  WHITE  LEAD 


97 


When  the  final  yellow  tinge  is  obtained,  it  is  probable 
that  some  of  the  immediately  preceding  test  drops  may 
have  developed  a  tinge  also.  If  such  is  the  case  deduct 
the  volume  of  two  drops  from  each  test  showing  a  color 
from  the  final  burette  reading. 

182.  Molybdate  solution.     Prepare  a  solution  of  am- 
monium molybdate  1  c.c.  of  which  is  equal  to  approxi- 
mately .01  gram  of  lead.     Standardize  against  a  weighed 
amount  of  chemically  pure  lead,  dissolving  in  nitric 
acid  and  treating  as  described  above. 

183.  Tannic  acid  solution.     Dissolve  0.5  gram  of  tannic 
acid  in  100  c.c.  of  water. 

184.  Carbon  dioxide.     The  amount  of  carbon  dioxide 
in  white  lead  can  be  most  accurately  estimated  by  means 
of  Knorr's  apparatus. 


FIG.  5.  —  KNORR'S  APPARATUS. 

This  apparatus  employs  only  ground-glass  joints,  and 
may  be  quickly  made  ready  for  use  or  taken  to  pieces 
and  packed  away.  On  the  other  hand,  it  is  inflexible 
and  must  be  carefully  handled.  A  is  a  distilling  flask 
fitted  to  a  condenser  by  a  ground-glass  stopper;  B,  reser- 
voir containing  acid;  C,  soda-lime  tube;  D,  condenser; 
E,  calcium  chloride  tube;  F,  U-tube  filled  with  pumice 


98  PAINT  AND  VARNISH  PRODUCTS. 

stone  moistened  with  sulphuric  acid,  followed  by  a 
calcium-chloride  tube  G.  The  three  soda-lime  tubes 
H,  H,  ff  are  followed  by  a  calcium  chloride  tube  K, 
which  is  connected  with  an  aspirator  at  L. 

The  calcium  chloride  and  soda  lime  employed  should 
be  finely  granulated  and  freed  from  dust  with  a  sieve. 

185.  One  gram  of   the  sample  to  be  examined  is 
placed  in  the  distilling  flask,  which  must  be  perfectly 
dry.     The  flask  is  closed  with  a  stopper  carrying  the 
tube  connecting  with  the  absorption  apparatus  and  also 
with  the  funnel  tube.     The  tubes  in  which  the  carbon 
dioxide  is  to  be  absorbed  are  weighed  and  attached  to 
the  apparatus.     In  case  two  Liebig  bulbs  are  employed, 
one  for  potassium  hydroxide  and  the  other  for  sulphuric 
acid,  to  absorb  the  moisture  given  up  by  the  potassium 
hydroxide  solution,  it  will  be  necessary  to  weigh  them 
separately.     If  soda-lime  tubes  are  employed  it  will  be 
found  advantageous  to  weigh  them  separately  and  fill 
the  first  tube  anew  when  the  second  tube  begins  to  in- 
crease in  weight  materially.     The  bulb   B  is  nearly 
filled  with  hydrochloric  acid  (sp.  gr.  1.1),  and  the  guard 
tube  C  placed  in  position.     The  aspirator  is  now  started 
at  such  a  rate  that  the  air  passes  through  the  Liebig 
bulbs  at  the  rate  of  about  two  bubbles  per  second. 
The  stopper  of  the  funnel  tube  is  opened  and  the  acid 
allowed  to  run  slowly  into  the  flask,  care  being  taken 
that  the  evolution  of  the  gas  shall  be  so  gradual  as  not 
materially  to  increase  the  current  through  the  Liebig 
bulb. 

186.  After  the  acid  has  all  been  introduced,  the  as- 
piration is  continued,  when  the  contents  of  the  flask  are 
gradually  heated  to  boiling,  the  valve  in  tube  B  being 
closed.     While  the  flask  is  being  heated  the  aspirator 
tube  may  be  removed,  although  many  analysts  prefer 


ANALYSIS  OF  WHITE  LEAD.  99 

when  using  ground-glass  joints  to  aspirate  during  the 
entire  operation.  The  boiling  is  continued  for  a  few 
minutes  after  the  water  has  begun  to  condense  in  Z), 
when  the  flame  is  removed,  the  valve  in  the  tube  B 
opened,  and  the  apparatus  allowed  to  cool  with  con- 
tinued aspiration.  The  absorption  tubes  are  then  re- 
moved and  weighed,  the  increase  in  weight  being  due  to 
carbon  dioxide. 

187.  When  extreme  accuracy  is  desired  the  carbon 
dioxide  after  passing  through  the  condenser  should  pass 
through  a  U-tube  filled  with  calcium  chloride,  a  U-tube 
filled  with  lumps  of  dehydrated  copper  sulphate  mois- 
tened with  sulphuric  acid  (sp.  gr.  1.84),  and  then  through 
a  U-tube  filled  with  pumice  stone  moistened  with  sul- 
phuric acid  before  being  absorbed  by  soda  lime.     The 
air  used  for  aspirating  should  also  pass  through  a 
large  U-tube  filled  with  soda  lime  before  passing  through 
the  small  soda-lime  tube  C.     In  order  to  make  the  ap- 
paratus compact  the  soda-lime  tubes  may  be  laid  side 
by  side  on  a  small  rack  constructed  for  the  purpose,  the 
soda-lime  tubes  being  connected  with  one  another  by 
small  U-shaped  glass  tubing  connections. 

188.  Acetic  acid  in  white  lead.1     "In  the  manufacture 
of  white  lead  by  any  process  involving  the  use  of  acetic 
acid,  a  certain  portion  of  the  acetic  acid  seems  to  be 
bound  firmly  so  that  it  cannot  be  washed  out  in  any 
ordinary  process  of  manufacture.     The  amount  of  the 
acetic  acid  which  is  fixed  by  the  white  lead  depends 
largely  upon  the  quantity  used  in  the  process  of  manu- 
facture.    The    navy    yard    specifications    demand    a 
white  lead  which  shall  not  contain  '  acetate  in  excess  of 
fifteen  one-hundredths  of  1  per  cent  of  glacial  acetic 
acid.'     It  seems  reasonable,  furthermore,  that  whether 

1  G.  W.  Thompson,  J.  Soc.  Chem.  Ind.,  Vol.  XXIV,  No.  9. 


100  PAINT  AND  VARNISH  PRODUCTS. 

the  acetic  acid  is  objectionable  or  not,  the  intelligent 
purchaser  of  white  lead  should  be  enabled,  as  far  as 
possible,  to  know  what  he  is  buying,  and  perhaps  to 
trace  back  results  to  some  definite  cause/' 

189.  "  Ordinary  lead  acetate  solution  will  take  up 
varying  amounts  of  lead  oxide  to  form  basic  lead  ace- 
tate.    The  more  concentrated  the  lead  acetate  solution 
is,  the  less  basic  will  be  the  formed  acetate ;  for  instance, 
the  ordinary  pharmacopoeia  solution  —  '  Liquor  Plumbi 
Subacetatis '  -  —  contains  two  equivalents  of  lead  to  one 
of  acetic  acid,  and,  while  this  solution  may  be  made 
more  basic  than  this  by  adding  an  excess  of  litharge,  the 
amount  of  litharge  which  it  will  take  into  solution  in 
excess  of  that  required  to  form  the  pharmacopoeia  solu- 
tion is  comparatively  small." 

190.  "  Working  with  dilute  solutions  of  lead  acetate, 
however,  solutions  can  be  obtained  containing  as  much 
as  ten  equivalents  of  lead  to  one  of  acetic  acid.     These 
very  basic  dilute  solutions  may,  however,  be  regarded 
by  some  as  supersaturated  solutions,  for  the  reason 
that  the  basic  lead  tends  to  separate  out  on  slight  provo- 
cation, carrying  with  it  some  acetic  acid.     If  this  very 
basic  lead  acetate  which  separates  out  is  washed  with 
distilled  water,  it  appears  to  form  a  colloidal  solution 
from  which  the  basic  lead  is  readily  precipitated  in  the 
presence  of  suspended  inert  material,  and  especially 
in   the  presence  of  electrolytes.      Ordinary  water  is 
usually  used  for  washing  white  lead,  and,  as  this  water 
contains  more  or  less  saline  substances,  any  of  this 
extremely  basic  acetate  that  is  present  will  be  precip- 
itated with  the  white  lead,  and  go  into  the  finished 
product." 

191.  Determination.     "18  grams  of  the  dry  white  lead 
are  placed  in  a  500-c.c.  flask,  this  flask  being  arranged 


ANALYSIS  OF  WHITE   LEAD-..  101 

for  connection  with  a  steam  supply,  and  also  with  an 
ordinary  Liebig  condenser.  To  this  white  lead  is  added 
40  c.c.  of  sirupy  phosphoric  acid,  18  grams  of  zinc  dust, 
and  about  50  c.c.  of  water.  The  flask  containing  the 
material  is  heated  directly  and  distilled  down  to  a  small 
bulk.  Then  the  steam  is  passed  into  the  flask  until  it 
becomes  about  half  full  of  condensed  water,  when  the 
steam  is  shut  off  and  the  original  flask  heated  directly 
and  distilled  down  to  the  same  small  bulk,  this  opera- 
tion being  conducted  twice.  The  distillate  is  then  trans- 
ferred to  a  special  flask  and  1  c.c.  of  sirupy  phosphoric 
acid  added  to  insure  a  slightly  acid  condition." 

192.  "The  flask  is  then  heated  and  distilled  down  to 
a  small  bulk  —  say  20  c.c.      Steam  is  then  passed 
through  the  flask  until  it  contains  about  200  c.c.  of  con- 
densed water,  when  the  steam  is  shut  off  and  the  flask 
heated  directly.     These  operations  of  direct  distillation 
and  steam  distillation  are  conducted  until  10  c.c.  of 
the  distillate  require  but  a  drop  of  N/10  alkali  to  pro- 
duce  a   change   in   the  presence   of  phenolphthalein. 
Then  the  bulk  of  the  distillate  is  titrated  with  N/10 
sodium  hydroxide,  and  the  acetic  acid  calculated.     It 
will  be  found  very  convenient  in  this  titration,  which 
amounts  in  some  cases  to  from  600  to  700  c.c.,  to  titrate 
the  distillate  when  it  reaches  200  c.c.,  and  so  continue 
titrating  every  200  c.c.  as  it  distills  over. 

193.  Conclusions.      "  The    details    in    this   described 
method,  as  regards  the  supply  of  steam  from  an  outside 
flask,  its  condensation  and  subsequent  evaporation,  are 
not  essential  to  the  process,  but  can,  of  course,  be  modi- 
fied so  as  to  conform  to  the  ordinary  method  of  distill- 
ing acetic  acid  from  acetate  of  lime.     If  the  white  lead 
contains  appreciable  amounts  of  chlorine,  it  is  well  to 
add  some  silver  phosphate  to  the  second  distillation 


102 


PAlfrT  AND  VARNISH  PRODUCTS. 


flask,  and  not  to  carry  the  distillation  from  this  flask 
too  far  at  any  time.  If  the  dry  white  lead  under  ex- 
amination has  been  obtained  by  the  extraction  as  a 
residue  from  white  lead  paste,  it  is  well  that  this  extrac- 
tion should  be  exceedingly  thorough,  as  otherwise  fatty 
acids  may  be  held  and  distilled  with  the  acetic  acid. 
Even  then  they  will  not  interfere  with  the  final  titra- 
tion,  as  they  may  be  filtered  from  the  distillate  before 
titration,  should  that  be  desired." 


194.  ANALYSES  OF  MISCELLANEOUS  WHITE  LEADS  MADE 
BY  THE  AUTHOR. 


No. 

Net 
Weight. 

White 
Lead. 

Lead 
Sul- 
phate. 

Zinc 
Oxide. 

Barytes 

Calcium 
Car- 
bonate. 

Silica. 

Clay. 

Unde- 
ter- 
mined. 

I 

13  5  oz. 

9  98 

12  00 

76  28 

1  10 

0  64 

II 

15.4  oz. 

64.73 

3  60 

30  43 

0  76 

0  48 

III 

IV 

v 

14.8oz. 
15.0  oz. 

4.69 
3.34 
54  69 



12.50 
8.96 
17  38 

75.72 
72.35 
25  57 

5.89 
4.52 

0.67 

'io.'83 

0.53 
6  36 

VI 

lib., 

3.29 

6.90 

89.81 

VII 

14.2oz. 
1  lb., 

10.69 

20.03 

69.28 

VIII 

14  oz. 
15  oz. 

5.31 

6.37 

13.68 

74.25 

0  39 

None  of  the  above  products  are  entitled  to  be  called 
white  lead.  Only  one  bore  the  name  of  the  company 
putting  out  the  product. 

195.  Short  weights  of  white  lead  packages.  All  the  white 
leads  and  so-called  white  leads,  examined  by  the  writer, 
have  been  found  to  be  short  weight.  That  is,  the  kegs 
supposed  to  contain  12|  pounds  will  actually  contain,  in 
each  eight  kegs  which  should  have  shown  100  pounds, 
only  83  to  89  pounds.  As  showing  to  what  extent  the 
different  so-called  white  leads  actually  varied  and  fell 
short  in  weight,  I  give  the  following  list : 


ANALYSIS  OF  WHITE   LEAD. 


103 


Number. 

Assumed  Weight. 

Net  Weight. 

I 

Lba. 

50 
12| 
12| 
12* 
25 
25 
121 
12| 

Lbs. 
46 
11 
10 
10 
21 
22 
10 
11 

Oz. 
0 
13 
6 
7 
12 
7 
0 
0 

II                                         ... 

Ill 

IV 

v     

VI      

VII 

VIII 

CHAPTER  XII. 

ANALYSIS  OF  SUBLIMED  WHITE  LEAD  AND  THE  ZINC 
PIGMENTS. 

196.  The  analysis  of  sublimed  white  lead.1     Lead  and 
Zinc  Oxide.     Weigh  1  gram  into  a  small  beaker,  add 
20  c.c.  of  10  per  cent  sulphuric  acid,  stir  well,  and  allow 
to  stand  10  minutes,  filter,  and  wash  slightly  with  dilute 
sulphuric  acid  on  filter. 

Residue.  Dissolve  through  filter  with  hot,  slightly 
acid  ammonium  acetate  solution,  wash  with  hot  water, 
and  dilute  to  200  c.c.  with  hot  water.  Add  a  slight 
excess  of  potassium  bichromate  solution  and  heat. 
Filter  on  Gooch  crucible,  wash  with  water.  Dry,  ignite, 
and  weigh  as  lead  chr ornate. 

Filtrate.  Add  about  2  grams  of  ammonium  chloride, 
heat  to  boiling,  add  excess  of  ammonia,  and  filter.  Re- 
ject residue.  Add  1  gram  of  microcosmic  salt  and  a 
very  slight  excess  of  acetic  acid.  Boil,  cool,  filter  on 
Gooch  crucible,  and  wash  with  water.  Ignite,  and 
weigh  as  zinc  pyrophosphate.  Calculate  to  zinc  oxide. 

197.  Sulphates.     Dissolve  0.5  gram  in  water  25  c.c., 
ammonia  10  c.c.,  hydrochloric  and  in  slight  excess. 

Dilute  to  200  c.c.  and  add  a  piece  of  aluminum  foil 
which  should  about  cover  the  bottom  of  the  beaker.  It 
is  important  that  this  be  held  at  the  bottom  by  a  glass 
rod.  Boil  gently  until  the  lead  is  precipitated.  Comple- 
tion of  this  is  shown  by  the  lead  ceasing  to  coat  or  cling 
to  the  aluminum.  Decant  through  a  filter,  pressing 

1  The  author  is  indebted  to  L.  S.  Hughes  of  the 
Lead  Company  for  this  method. 

104 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      105 

the  lead  sponge  into  a  cake  to  free  it  from  solution. 
Add  to  filtrate  a  little  sulphur-free  bromine  water,  boil, 
and  precipitate  as  barium  sulphate  in  the  usual  manner. 

198.  Sulphur  dioxide.     Treat  2  grams  with  5  per  cent 

N 

sulphuric  acid  and  titrate  with  — — -  iodine.     A  quick 

100 

method  of  calculating  the  lead  sulphate  and  oxide  from 
the  above  data  is  the  following :  Multiply  the  weight  of 
barium  sulphate  from  1  gram  by  1.3,  which  gives  the 
weight  of  lead  sulphate.  Multiply  the  same  weight  of 
barium  sulphate  by  0.088  and  deduct  this  result  from 
the  total  lead  found.  Multiply  the  difference  by  1.077, 
which  will  give  the  lead  oxide. 

199.  Composition  of   sublimed  white  lead.     The  ap- 
proximate composition  of  sublimed  lead  as  stated  by 
the  manufacturers  is  as  follows: 

Per  cent. 

Lead  sulphate 75 

Lead  oxide 20 

Zinc  oxide 5 

100 

The  lead  sulphate  and  lead  oxide  are  apparently  com- 
bined as  a  white  oxysulphate.  The  zinc  oxide  is  inci- 
dental to  the  manufacture. 

ANALYSES  OF   SUBLIMED  WHITE  LEAD   BY  THE 
AUTHOR. 

I.  II. 

Per  cent.          Per  cent. 

Lead  sulphate 75.02  80.29 

Lead  oxide 18.48  14.46 

Zinc  oxide 6 . 22  5 . 18 

Silica  and  alumina 0.28  0.07 

100.00         100.00 

200.  Sublimed  blue  lead.     This  pigment,  which  has  a 
grayish  blue  color,  is  obtained  in  much  the  same  way 
as   sublimed   white  lead.     Its   variable   and   complex 


106  PAINT  AND  VARNISH  PRODUCTS. 

composition,  however,  limits  its  use.     The  following  is 
an  analysis  published  by  Mannhardt:1 

Per  cent. 

Lead  sulphate 41.72 

Lead  sulphite ' 7.55 

Lead  sulphide 10 . 76 

Lead  oxide.    ; 29.03 

Zinc  oxide 2.84 

Calcium  oxide   .    .    . 2 . 88 

Magnesium  oxide 0 . 80 

Ferric  oxide 0 . 40 

Carbon  dioxide 0.86 

Carbon 2.50 

Bitumen :  .    .  0.34 

Moisture    .                   0.50 


100.18 

201.  The  identification  and  estimation  of  sublimed  white 
lead  in  mixtures.2     Neutral  ammonium  chloride  solution 
will  dissolve  the  lead  compounds  of  sublimed  white  lead ; 
also  the  hydrate  of  corroded  white  lead,  zinc  oxide,  and 
some  calcium  sulphate.     It  leaves  undissolved  calcium 
carbonate,  zinc  sulphide,  normal  lead  carbonate,  and 
the  content  of  lead  carbonate  in  corroded  lead. 

To  determine  the  sublimed  white  lead  in  a  pigment 
containing  the  above  ingredients,  boil  the  sample  with 
a  considerable  excess  of  strong  neutral  ammonium  chlo- 
ride solution,  filter  hot  on  the  pump,  and  wash  with  hot 
dilute  neutral  ammonium  chloride. 

202.  The  lead,  zinc,  lime,  and  sulphuric  anhydride  are 
determined  in  the  filtrate.     The  required  sulphur  tri- 
oxide  is  combined  with  the  lime  and  the  rest  with  the 
lead.     Any  excess  of  lead  is  contingent  in  its  application 
upon  the  amount  of  lead  found  undissolved  by  the 
ammonium  chloride. 

If  there  is  an  appreciable  amount  of  this  residual 
carbonate,  the  required  hydrate  is  calculated,  and  a 

1  Drugs,  Oils  and  Paints,  August,  1909. 

2  The  author  is  indebted  to  L.  S.  Hughes  for  this  method. 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      107 

deduction  made  from  the  excess  lead  found  in  the  nitrate. 
Any  lead  in  the  original  nitrate  not  satisfied  is  now  cal- 
culated to  lead  oxide  and  regarded  as  the  lead  oxide  of 
sublimed  white  lead,  and  the  lead  sulphate  and  zinc 
oxide  thereof  calculated  and  deducted  from  the  total  of 
these  compounds. 

It  will  be  noted  that  the  conditions  above  considered 
are  much  more  complex  than  need  be  anticipated  in  the 
analysis  of  actual  paints. 

Extraction  of  lead  sulphate  by  the  above  treatment 
prevents  the  necessity  of  considering  the  sulphuric  an- 
hydride of  possible  barium  sulphate,  and  leaves  the 
original  residue  in  such  shape  that  if  it  contains  both 
the  carbonate  and  sulphate  of  barium  they  can  be  con- 
veniently separated. 

Analysis  of  Zinc  Pigments. 

203.  Moisture.     Two    grams    of    the    pigment    are 
weighed  out  on  a  watch  glass,  provided  with  a  cover 
glass  and  clip,  dried  for  two  hours  in  a  steam  oven,  the 
cover  glass  placed  in  position  and  held  by  the  clip,  'the 
glasses  cooled   in  the  desiccator  and  weighed.     Loss 
in  weight  represents  the  amount  of  moisture  in  the 
pigment. 

204.  Silica.    Weigh  1  gram  of  pigment  into  a  250-c.c. 
covered   beaker,  add  25   c.c.  of  concentrated  hydro- 
chloric  acid,   heat  gently  for  five  minutes,   or  until 
the  pigment  has  dissolved  (if  lead  sulphate  is  present 
in  considerable  quantity  this  may  take  quite  a  few 
minutes),  add   50   c.c.  hot  water,  and   continue  the 
heating  for  about  five  minutes  longer.     Filter  boiling 
hot  with  the  aid  of  suction,  washing  thoroughly  with 
boiling  water  so  as  to  remove  all  the  lead  and  zinc 
salts  from  the  filter  paper.     The  filter  paper  and  any 


108  PAINT  AND  VARNISH  PRODUCTS. 

residue  of  silica  is  burned,  ignited,  and  weighed  in  the 
usual  manner.  Any  weighable  residue  is  reported  as 
silica. 

205.  This  treatment  may  give  results  that  are  slightly 
low,  owing  to .  the  slight  solubility  of  silica  in  strong 
hydrochloric  acid,   but  for  commercial  purposes  this 
slight  error  may  be  neglected.     In  carefully  prepared 
zinc  pigments  the  amount  of  silica  present  will  be  un- 
weighable;  even  with  careless  processing  the  amount 
will  seldom  exceed  a  very  few  hundredths  of  1  per 
cent. 

206.  Sulphur  dioxide.     Weigh  3  grams  of  the  pigment 
into  a  250-c.c.  beaker;  add  100  c.c.  of  distilled  water, 
that  has  been  recently  boiled  and  cooled.     Add  5  c.c.  of 
concentrated  sulphuric  acid,  stir  thoroughly,  and  allow 
to  stand   15  minutes.      Titrate  with  standard   hun- 
dredth normal  iodine  solution,  using  starch  paste  as 
an  indicator. 

1  c.c.  hundredth  normal  iodine  =  0.00032  gram  sul- 
phur dioxide. 

207.  Preparation  of  reagents  —  Iodine  solution.     Dis- 
solve 1.268  grams  of  pure  iodine  and  1.8  grams  of  po- 
tassium iodide  in  about  150  c.c.  of  water  in  a  graduated 
liter  flask.     After  solution,  fill  to  the  mark  with  water 
that  has  been  freshly  boiled. 

208.  Sodium  thiosulphate.     Dissolve  2.5  grams  in  re- 
cently boiled  distilled  water  and  make  up  to   1  liter. 
Preserve  in  a  brown  glass  bottle  or  one  that  has  received 
a  liberal  coat  of  asphaltum. 

209.  Starch  paste.     One  gram  of  starch  is  boiled  in 
200  c.c.  of  distilled  water. 

210.  Standardizing   the    sodium   thiosulphate    solution. 
Pipette  20  c.c.  of  standard  potassium  dichromate  solu- 
tion in  a  250-c.c.  beaker;  add  10  c.c.  of  a  15-per  cent 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.     109 

solution  of  potassium  iodide.  Add  10  c.c.  of  a  15-per 
cent  solution  of  potassium  iodide.  Add  to  this  5  c.c. 
of  strong  hydrochloric  acid.  Allow  the  solution  of  thio- 
sulphate  to  run  in  slowly  from  a  burette  until  the  yellow 
color  has  almost  disappeared.  Add  a  few  drops  of 
starch  paste  and  continue  the  addition  of  thiosulphate 
with  constant  stirring  until  the  blue  color  just  disap- 
pears. The  burette  reading  is  then  made  and  the 
value  of  the  thiosulphate  calculated. 

211.  Standard  of  acceptance.     A  good  grade  of  zinc 
oxide  should  contain  only  a  trace  of  sulphur  dioxide. 
Many  paint  chemists  reject  oxides  containing  more  than 
six  hundredths  of  one  per  cent.     The  reason  for  this  is 
that  the  sulphur  dioxide  affects  the  character  of  the 
linseed  oil  very  strongly,  causing  the  paint  to  thicken 
and  ultimately  " liver"  in  the  package.     This  may  be 
shown  in  an  experimental  way  by  dividing  a  sample  of- 
zinc  oxide  into  two  parts,  exposing  one  part  to  an  at- 
mosphere  of   sulphur   dioxide,    then   spreading   equal 
amounts  of  both  samples  on  a  glass  plate  and  mixing 
to  a  paste  with  the  same  number  of  drops  of  oil  in  ex- 
actly the  same  manner.     It  will  be  found  that  the 
sample  containing  the  sulphur  dioxide  will  be  thicker 
and  stiffer  than  the  other,  showing  the  effect  of  the 
sulphur  dioxide  on  the  oil. 

212.  Reaction  with  rosin  products.     In  the  presence  of 
rosin  products  of  any  kind,  such  as  are  often  used  in  the 
driers  of  mixed  paints,  sulphur  dioxide  acts  as  a  contact 
agent  of  great  strength,  causing  changes  all  out  of  pro- 
portion to  the  amount  present,  often  resulting  in  hard- 
ening, " washing"  of  the  paint  film,  "livering"  in  the 
package,  etc.     These  results  will  be  influenced  to  a 
considerable    degree    by   the    acidity,    moisture,    and 
temperature  of  the  paint,  and  hence  no  hard  and  fast 


110  PAINT  AND  VARNISH  PRODUCTS. 

deductions  can  be  made  as  to  what  may  be  expected 
of  any  particular  paint  containing  sulphur  dioxide  in 
excess  of  the  prescribed  amount. 

213.  Zinc  sulphate.     Ten  grams  of  the  pigment  are 
weighed  into  a  250-c.c.  Erlenmeyer  flask  and  100  c.c.  of 
boiling  water  added.     The  contents  of  the  flask  are  then 
shaken  thoroughly  for  several  minutes  and  filtered  and 
the  residue  on  the  filter  paper  washed  with  several  por- 
tions of  boiling  water.     The  soluble  zinc  in  the  filtrate 
is  then  titrated  as  described  under  the  "  Estimation  of 
Zinc  "  by  titration  with  ferrocyanide,  and  calculated  to 
zinc  sulphate. 

214.  It  is  not  advisable  to  boil  zinc  oxide  pigments 
with  the  water,  as  interaction  may  occur  between  the 
zinc  oxide  and  any  lead  sulphate  present,  resulting  in 
the  formation  of  more  zinc  sulphate.     Neither  is  it  wise 
.to  estimate  the  soluble  combined  sulphuric  acid  in  the 
hot  aqueous  filtrate  and  calculate  to  zinc  sulphate,  as 
there  often  seems  to  be  an  excess  over  what  is  required 
to  form  the  normal  sulphate  of  zinc  and  hence  the  re- 
sults are  apt  to  be  too  high. 

215.  Effect.    Zinc  sulphate  is  not  considered  by  many 
paint  chemists  to  be  so  objectionable  in  zinc  pigments 
as  sulphur  dioxide,  and  is  often  permitted  in  amounts 
under  1  per  cent.     In  amounts  above   1  per  cent  it 
seems  to  act  as  an  astringent  on  the  oil  when  used  in 
the  preparation  of  mixed  paints,  tending  to  prevent  the 
proper  penetration  of  the  wood,  especially  if  the  paint 
has  been  ground  for  some  length  of  time.     A  prominent 
paint  chemist  discusses  its  effect  as  follows:  "The  action 
of  zinc  sulphate  is  twofold :  first,  as  an  astringent  upon 
the  oil  and  tending  to  cause  a  distinct  demarcation 
between  two  coats ;  and  second,  that  of  a  contact  agent, 
facilitating  reaction   between   the  different  pigments. 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      Ill 

The  visible  results  of  its  presence  are  peeling  and  'wash- 
ing.' Apparently,  rather  more  than  the  normal  amount 
of  moisture  must  be  present  to  cause  its  activity,  and  if 
the  paint  coat  has  set  under  dry  or  normal  conditions, 
the  zinc  sulphate  produces  no  apparent  effect."  In  the 
exposure  tests  conducted  by  the  author,  the  worst  cases 
of  "washing"  have  occurred  with  zinc  pigments  in 
which  the  sulphur  dioxide  was  less  than  one-hundredth 
of  1  per  cent  and  the  zinc  sulphate  between  1  and  li 
per  cent. 

216.  Lead.     The  lead  present  in  zinc  pigments  is  usu- 
ally in  the  form  of  sulphate  and  may  be  estimated  by 
either  of  the  following  methods. 

217.  Method  I.   The  filtrate  from  the  silica,  which  need 
not  exceed  100  c.c.  in  volume  if  the  washing  has  been 
judiciously  conducted  by  suction  or  the  hydrochloric 
acid  solution  is  absent,  is  evaporated  very  nearly  to 
dryness  in  an  uncovered  beaker  on  the  hot  plate,  avoid- 
ing actual  boiling,  10  c.c.  of  warm  water  added,  and 
evaporated  again  nearly  to  dryness  in  order  to  expel 
the  hydrochloric  acid.     Cool,  add  30  c.c.  dilute  sul- 
phuric acid,  heat  to  boiling  for  five  minutes  in  a  covered 
beaker,  cool,  add  50  c.c.  of  alcohol,  and  allow  to  stand 
one-half  hour  or  until  all  of  the  lead  sulphate  is  precipi- 
tated from  solution.     Filter  through  a  weighed  Gooch 
crucible,  washing  thoroughly  with  50  per  cent  alcohol, 
until  the  precipitate  is  entirely  freed  from  zinc  sulphate. 
Dry  on  hot  plate,  heat  gently  over  a  Bunsen  burner, 
cool  in  desiccator,   and  weigh  as  lead  sulphate.     If 
heated  over  the  flame  before  drying,  a  portion  of  the 
lead  is  liable  to  be  reduced  to  lead  oxide  by  the  alcohol, 
and  the  weight  will  be  low. 

218.  Method  II.     The  lead  may  be  separated  from  the 
zinc  in  a  solution  barely  acid  with  hydrochloric  acid,  by 


112  PAINT  AND  VARNISH  PRODUCTS. 

hydrogen  sulphide,  the  precipitated  lead  sulphide  dis- 
solved in  nitric  acid  and  titrated  with  standard  molyb- 
date  or  bichromate  solution,  as  described  in  Chapter 
XVI,  Analysis  of  White  Paints. 

219.  Method  III.    The  amount  of  lead  sulphate  may 
be  rapidly  estimated  by  dissolving  a  weighed  amount  of 
the  pigment  in  dilute  acetic  acid,   filtering  on  to  a 
weighed  Gooch  crucible,  washing  with  warm  water, 
heating  gently,  and  weighing  the  lead  sulphate  direct. 
Lead  sulphate  being  slightly  soluble  in  acetic  acid  the 
results  will  be  somewhat  low  and  can  only  be  consid- 
ered as  roughly  approximate. 

220.  Total   zinc.      The   zinc  can  be  rapidly  and  ac- 
curately  estimated  volume  trie  ally    by   the  following 
methods. 

221.  Potassium  ferrocyanide  method.     Preparation  of 
reagents. 

222.  Standard  zinc    solution.     Dissolve    10   grams   of 
chemically  pure  zinc  in  hydrochloric  acid  in  a  gradu- 
ated liter  flask,  add  50  grams  of  ammonium  chloride, 
and  make  up  to  1  liter. 

1  c.c.  =  0.01  gram  zinc  or  0.01245  gram  zinc  oxide. 

223.  Standard   potassium   ferrocyanide    solution.     Dis- 
solve 46  to  48  grams  of  crystallized  potassium  ferrocya- 
nide in  water,  make  up  to  1000  c.c. 

224.  Uranium  nitrate  solution.     Dissolve  15  grams  of 
uranium  nitrate  in  100  c.c.  of  water. 

225.  Standardizing  the  ferrocyanide  solution.     To  de- 
termine the  value  of  the  potassium  ferrocyanide  solu- 
tion, pipette  25  c.c.  of  the  zinc  solution  into  a  400-c.c. 
beaker.     Dilute  somewhat  and  make  faintly  alkaline 
with  ammonia,  bring  to  a  faintly  acid  condition  with 
hydrochloric  acid,  and  then  "add  3   c.c.  excess  of  the 
concentrated  acid,  dilute  to  a  total  volume  of  about 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      113 

250  c.c.,  heat  to  80°  C.,  and  titrate  as  follows:  Pour  off 
about  10  c.c.  of  the  zinc  solution  into  a  small  beaker 
and  set  aside,  run  the  ferrocyanide  into  the  remainder 
from  a  burette,  a  few  cubic  centimeters  at  a  time, 
until  the  solution  takes  on  a  slight  ash-gray  color,  or 
until  a  drop  of  the  solution  placed  in  contact  with  a 
drop  of  the  uranium  nitrate  solution  on  a  porcelain 
plate  turns  to  a  distinct  brownish  color. 

226.  Often  the  end  point  has  been  passed  by  quite  a 
little.     The  10  c.c.  of  zinc  solution  that  has  been  re- 
served is  now  added  and  the  titration  continued,  drop 
by  drop,  testing  a  drop  of  the  solution  carefully  on 
the  porcelain  plate  after  each  addition  of  ferrocyanide 
solution.     Some   little   time  is   required  for   the   test 
drop  to  change  color,  so  that  the  end  point  may  have 
been  passed  slightly;  this  may  be  corrected  for  by 
making  a  memorandum  of  the  burette  readings,  having 
the  test  drops  arranged  in  regular  order,  and  taking  as 
the  proper  reading  the  one  first  showing  a  distinct 
brownish  tinge.     Having  noted  the  number  of  cubic 
centimeters  ferrocyanide  required  for  the  titration  of 
the  standard  zinc  solution,  the  value  of  1  c.c.  may  be 
readily  calculated. 

227.  Titration  of  sample.     One-half  gram  of  the  sample 
if  high  in  zinc,  or  1  gram  if  the  zinc  content  is  fairly  low, 
is  dissolved  in  a  covered  beaker  in  10  c.c.  of  hydro- 
chloric acid  and  10  c.c.  of  water,  the  solution  diluted 
somewhat,  neutralized  with  ammonia,  and  treated  ex- 
actly as  described  above  for  the  standard  zinc  solution, 
care  being  taken  to  titrate  to  exactly  the  same  depth 
of  color  on  the  porcelain  test  plate.     If  the  method  is 
carefully  carried  out,  the  procedure  being  uniformly 
the  same  in  each  determination,  the  results  will  be 
found  satisfactorily  accurate. 


114  PAINT  AND  VARNISH  PRODUCTS. 

228.  Combined  sulphuric  acid.     Dissolve  0.5  gram  to 
1  gram  of  the  pigment,  according  to  the  amount  of 
sulphates  present,  in 

Water,  25  c.c. 

Ammonia,  10  c.c. 

Hydrochloric  acid,  a  slight  excess. 

229.  Dilute  to  200  c.c.  and  add  a  disk  of  aluminum 
foil,  which  should  about  cover  the  bottom  of  the  beaker. 
Boil  gently  until  the  lead  is  precipitated,  holding  the 
disk  if  necessary  to  the  bottom  of  the  beaker  with  a 
glass  rod.     The  completion  of  precipitation  is  shown 
by  the  lead  ceasing  to  coat  or  cling  to  the  aluminum. 
Decant  through  a  filter,  pressing  the  lead  sponge  into 
a  cake  and  washing  thoroughly  to  free  from  solution. 

230.  Add  to  the  filtrate  a  few  drops  of  bromine  water, 
boil,  and  precipitate  with  barium  chloride  in  the  usual 
manner  for  sulphates.     In  order  to  avoid  a  possible 
reduction  of  a  portion  of   the  barium  sulphate  in  the 
pores  of  the  filter  paper  during  its  incineration,  the 
precipitate  may  be  filtered  directly  on  to   a  Gooch 
crucible,  which  after  being  weighed  has  a  disk  of  ash- 
less  filter  paper  placed  on  top  of  the  customary  asbestos 
felt.     This  will  effectually  prevent  any  of  the  precipi- 
tate from  burrowing  through  the  filter.     The  ignition 
of   the   precipitate   in  the  presence  of  the  small  disk 
of  filter  paper  will  cause  no  appreciable  reduction  to 
sulphide. 

231.  Calculations.     The  amount  of  zinc  present  as  sul- 
phate of  zinc  is  deducted  from  the  total  zinc  and  the 
remainder  calculated  to  zinc  oxide.     The  sulphuric  acid 
combined  with  the  zinc  is  deducted  from  the  total  com- 
bined sulphuric  acid  and  the  remainder  calculated  to 
lead  sulphate.     Any  excess  of  lead  over  that  required 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      115 

to  combine  with  the  sulphuric  acid  is  calculated  to 
lead  oxide.  Unless  sublimed  lead  is  present  there  will 
be  little  or  no  lead  oxide. 

Undoubtedly  new  sulphate  of  lead  pigments  will  be 
placed  on  the  market  within  the  next  few  years  which 
will  be  entirely  different  from  those  discussed,  and  in 
such  instances  careful  determinations  of  the  service 
values  should  be  made  apart  from  the  chemical  exam- 
ination. 


CHAPTER  XIII. 

ANALYSIS  OF  SUBLIMED  WHITE  LEAD  AND  THE  ZINC 
PIGMENTS  (continued). 

232.  Zinc  white.  It  was  formerly  the  custom  to  offer 
reduced  zinc  oxides  in  oil,  i.e.,  combination  zincs  under 
the  name  of  zinc  white,  the  different  grades  being  dis- 
tinguished by  the  use  of  such  terms  as  "  Green  Seal, 
Red  Seal,"  etc.  Until  the  passage  of  suitable  paint 
laws  the  purchaser  had  no  means  of  knowing  what  he 
was  obtaining,  any  more  than  he  did  in  the  case  of 
combination  leads  which  had  hitherto  been  sold  under 
the  simple  designation  white  lead.  It  is  now  customary 
for  paint  manufacturers  to  offer  reduced  zinc  oxides 
under  an  explanatory  designation  like  the  following: 

Zinc  White. 

In  combination  with  reinforcing  pigments.  Ground 
in  pure  linseed  oil.  12|  Ibs.  net  weight. 

Analysis.  Per  cent. 


100.00 

233.  The  analysis  of  reduced  zinc  oxides  offers  no 
difficulties  except  that  when  ground  in  varnish  the 
determination  of  the  constitution  of  the  varnish  will 
require  careful  consideration.  Usually  the  varnish  will 
be  found  to  be  dammar  cut  with  turpentine  or  naph- 
tha or  both,  and  may  be  used  in  conjunction  with 
varnish  oil  (a  specially  prepared  linseed  oil). 

116 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      117 

234.  The  following  analyses  are  characteristic  of  the 

zinc  whites  on  the  market : 

i.  n.  in. 

Per  cent.  Per  cent.  Per  cent. 

Zinc  oxide 53.93  69.61  61.83 

Barium  sulphate 35.96  18.99  8.03 

Linseed  oil 10.11  11.40  2.00 

Turpentine 14 . 35 

Dammar  gum 13 . 79 

100.00         100.00         100.00 

235.  Estimation  of  arsenic  and  antimony  in  zinc  leads. 
Weigh  2  grams  of  the  sample  into  a  200-c.c.  digestion 
flask.     Add  7  grams  of  potassium  bisulphate,  0.5  gram 
of  tartaric  acid,  and  10  c.c.  of  concentrated  sulphuric 
acid.     Digest  carefully  at  first,  but  finally  with  the 
full  power  of  a  Bunsen  burner  until  a  clear  mass  re- 
mains, containing  but  little  free  sulphuric  acid.     Cool, 
spreading  the  melt  around  on  the  sides  of  the  flask. 
Add  50  c.c.  of  water,  10  c.c.  of  strong  hydrochloric  acid, 
and  digest  for  about  twenty  minutes  without  boiling. 

236.  Cool  thoroughly  under  the  tap  and  filter  off  the 
separated  lead  sulphate.     Dilute  the  filtrate  to  about 
300  c.c.  with  hot  water,  maintain  the  liquid  warm,  and 
pass  in  hydrogen  sulphide  for  about  fifteen  minutes  or 
until  precipitation  is  complete.     Filter,  washing  with 
hydrogen  sulphide  water.     Digest  filter  and  contents 
in  a  rather  small  amount  of  yellow  ammonium  sul- 
phide.    Filter  on  suction  cone,  washing  with  as  small 
a  quantity  of  water  as  possible. 

237.  Digest  the  filtrate  with  3  grams  of  potassium 
*  bisulphate  and  10  c.c.  of  strong  sulphuric  acid  over  a 

free  flame  until  all  of  the  free  sulphur  and  the  larger 
portion  of  free  acid  are  expelled.  Cool,  spreading  the 
melt  around  on  the  sides  of  the  flask  as  before.  Add 
25  c.c.  of  water  and  10.  c.c.  of  strong  hydrochloric  acid, 
and  warm  to  effect  complete  solution.  Cool  under  the 


118  PAINT  AND  VARNISH  PRODUCTS. 

tap,  add  40  c.c.  of  strong  hydrochloric  acid,  and  pass 
in  hydrogen  sulphide  until  complete  precipitation  of 
the  arsenic  takes  place,  — 15  to  30  minutes.  The 
antimony  remains  in  solution. 

238.  Filter  off  the  precipitated  arsenious  sulphide  on 
to  a  weighed  Gooch  crucible,  washing  with  a  mixture  of 
two  volumes  of  hydrochloric  acid  and  one  of  water. 
The  filtrate  is  reserved  at  this  point  for  the  estimation 
of  antimony.     The  precipitate  is  next  washed  with 
alcohol,  the  crucible  and  contents  placed  in  a  small 
beaker,   the  crucible  nearly  filled  with  carbon  bisul- 
phide, (and  the  contents  allowed  to  digest  at  ordinary 
temperature  for    about    twenty  minutes  in   order   to 
dissolve  the  free  sulphur.     The  carbon  bisulphide  is 
removed  by  suction,  the  crucible  dried  in  the  steam 
oven,  cooled,  and  the  precipitate  weighed  as  arsenious 
sulphide  and  calculated  to  arsenious  oxide. 

Weight  arsenious  sulphide  X  0.8043  =  weight  arse- 
nious oxide. 

239.  Instead  of  weighing  as  the  sulphide,  the  arsenic 
may  be  estimated  volumetrically  as  follows:  Wash  out 
the  hydrochloric   acid  from  the  sulphide  precipitate 
with  hydrogen  sulphide  water.     Digest  filter  and  con- 
tents in  a  little  warm  ammonium  sulphide,  filter  on  a 
suction  cone,  washing  with  a  little  dilute  ammonium 
sulphide  solution.     Place  the  filtrate  in  digestion  flask, 
add  2  to  3  grams  of  potassium  bisulphate  and  5  c.c.  of 
strong  sulphuric  acid.     Evaporate,  boiling  to  a  small 
bulk,  and  then  manipulate  the  flask  over  a  free  flame 
until  the  sulphur  is  entirely  expelled  and  most  of  the 
free  acid  also.     Take  up,  after  cooling,  by  warming 
with  50  c.c.  of  water,  and  then  boil  sufficiently  to  expel 
any  possible  sulphur  dioxide.     Now  drop  in  a  bit  of 
litmus  paper  as  an  indicator,  and  then  add  ammonia 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      119 

until  the  solution  is  slightly  alkaline.  Again  slightly 
acidify  with  hydrochloric  acid  and  cool  to  room  tem- 
perature. Finally,  add  3  to  4  grams  of  sodium  acid 
carbonate  and  a  little  starch  liquor  and  titrate  with 
standard  iodine  solution.  Pay  no  attention  to  a  slight 
discoloration  toward  the  end,  but  proceed  slowly  until 
a  single  drop  of  the  iodine  produces  a  strong  permanent 
blue  color. 

240.  Preparation  of  iodine  solution.    The  iodine  solu- 
tion may  be  prepared  by  dissolving  about  11  grams  of 
iodine  in  a  little  water  with  the  addition  of  about  20 
grams  of  potassium  iodide   and  diluting  to   1   liter. 
Standardize  with  arsenious  oxide.     Dissolve  about  0. 150 
gram  in  5  c.c.  of  strong  hydrochloric  acid  by  warming 
very  gently,  dilute  and  neutralize  as  described  above, 
and  finally  titrate  with  the  iodine  solution.     1  c.c.  of 
the  latter  will  equal  about  0.003  gram  of  arsenic. 

241.  Antimony.     Very  nearly  neutralize   the   filtrate 
reserved  for  the  antimony  estimation  with  hydrochloric 
acid,  dilute  with  double  its  volume  of  hot  water,  and 
pass  in  hydrogen  sulphide  until  all  of  the  antimony  is 
precipitated.     Filter,  washing  with  hydrogen  sulphide 
water.     Digest  filter  and  contents  in  a  little  ammonium 
sulphide,  filter  on  suction  cone,  and  wash  with  dilute 
ammonium  sulphide.     Place  the  filtrate  in  the  diges- 
tion flask  and  add  about  3  to  4  grams  of  (pure)  potas- 
sium bisulphate  and  10  c.c.  of  strong  sulphuric  acid. 
Boil  as  previously  described  to  expel  first  the  water, 
then  all  the  free  sulphur,  and  finally  most  of  the  free 
acid. 

242.  Cool,  add  50  c.c.  of  water  and  10  c.c.  of  strong 
hydrochloric  acid.    Heat  to  effect  solution,  and  then  boil 
for  a  few  minutes  to  expel  any  possible  sulphur  dioxide 
Finally    add    10    c.c.    more    of    strong    hydrochloric 


120  PAINT  AND  VARNISH  PRODUCTS. 

acid,  cool  under  the  tap,  dilute  to  about  200  c.c.  with 
cold  water,  and  titrate  with  a  standard  solution  of 
potassium  permanganate.  The  solution  ordinarily  used 
for  iron  titrations  will  answer.  The  oxalic  acid  value 
of  the  permanganate  multiplied  by  0.9532  will  give  the 
antimony  value. 

243.  Methods  of  determining  small  amounts  of  arsenic 
and  antimony  in  use  at  Canon  City,  Colorado.   Method  I. 
Take  two  or  three  grams  of  pigment  and  dissolve  in 
10  c.c.  nitric  acid  and  10  c.c.  sulphuric  acid.     Heat  to 
expel  the  nitric  acid  and  evaporate  to  sulphuric  fumes. 
The  advantage  of  the  nitric  acid  is  to  oxidize  the  arsenic 
present  and  thereby  avoid  any  loss  of  arsenious  acid 
by  volatilization.     Allow  to  cool  and  dilute  with  cold 
water,  then  add  about  50  per  cent  of  the  volume  of 
alcohol  to  insure  complete  precipitation  of  all  lead  as 
lead  sulphate.     Filter  and  wash,  boil  filtrate  to  expel 
alcohol,  and  add  about  10  to  15  c.c.  of  hydrochloric 
acid.      Precipitate  the  warm  solution  with  hydrogen 
sulphide.      Filter  and  wash  with  dilute  hydrogen  sul- 
phide water.     All  arsenic,  antimony,  and  copper  are 
on  the  filter  as  sulphides.     Test  filtrate  with  hydrogen 
sulphide  as  check  on  precipitation. 

244.  Dissolve  the  sulphides  in  caustic  potash  solu- 
tion, then  bring  to  a  boil  and  pass  hydrogen  sulphide 
into  warm  solution  as  before.     Filter  and  test  filtrate. 
Wash  with  dilute  ammonium  sulphide  solution.     All 
arsenic  and  antimony  are  in  filtrate  and  any  copper 
present  is  on  the   filter.     If  any   copper  is  present, 
dissolve  and  titrate  by  the  iodide  method. 

245.  Make  filtrate  acid  with  hydrochloric  acid  and 
add  about  10  c.c.  excess  and  pass  in  hydrogen  sulphide 
gas  as  before.     Filter  off  the  sulphides  of  arsenic  and 
antimony  and  wash  with  hydrogen  sulphide  water. 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      121 

Dissolve  these  sulphides  in  about  10  c.c.  aqua  regia, 
then  dilute  with  water  and  make  alkaline  with  ammo- 
nia, adding  about  25  c.c.  excess.  Then  add  from  1 
to  2  grams  tartaric  acid  and  10  to  15  c.c.  magnesia 
mixture.  Allow  to  stand  over  night.  All  the  arsenic 
is  precipitated  as  ammonium  magnesium  arsenate. 
Antimony  remains  in  solution,  being  held  there  by  the 
tartaric  acid  present.  Filter  off  the  ammonium  mag- 
nesium arsenate,  washing  with  cold  water  containing 
a  little  ammonia,  then  dry,  ignite,  and  weigh  as  mag- 
nesium pyroarsenate. 

246.  Acidify  the  filtrate  with  hydrochloric  acid  and 
precipitate  the  antimony  with  hydrogen  sulphide  as 
before;  filter  and  wash  with  hydrogen  sulphide  water. 
Separate  the  antimony  sulphide  from  the  filter  paper 
and  dissolve  the  adhering  particles  with  ammonium 
sulphide,  transferring  to  a  beaker.     Wash  with  ammo- 
nia and  evaporate  to  dryness  on  water  bath.     Carefully 
add  a  few  drops  of  nitric  acid  and  1  to  2  c.c.  of  fum- 
ing nitric  acid  to  oxidize  the  antimony.     Evaporate  to 
small  bulk  for  crucible,  and  heat  to  dryness  in  water 
bath,  ignite  at  low  red  heat  to  constant  weight. 

247.  Method  II.     Treat  10  grams  of  pigment  in  a  No. 
3-A  casserole  with  about  10  grams   potassium  bisul- 
phate,  10  c.c.  nitric  acid,  15  c.c.  sulphuric  acid,  and 
about  0.5  gram  tartaric  acid.     Run  to  strong  fumes; 
continue  heating  until  all  the  carbon  is  destroyed  and 
the  solution  is  clear.     Cool,  dilute,  and  boil  until  sol- 
uble sulphates  are  in  solution.     Cool,  filter,  and  wash 
thoroughly.     Add  tartaric  acid  and  pass  hydrogen  sul- 
phide gas.     Filter  off  arsenic  and  antimony  sulphides. 
Dissolve  precipitate  in  potassium  hydroxide  solution 
and  filter.     Pour  filtrate  into  solution  of  hydrochloric 
acid  (2  to  1).     Pass  hydrogen  sulphide  gas  and  filter 


122  PAINT  AND  VARNISH  PRODUCTS. 

off  As2S3  on  a  weighed  Gooch  crucible.     Wash  with 
alcohol  and  carbon  bisulphide  to  remove  sulphur. 

248.  Neutralize  filtrate  until  Sb2S3  begins  to  precipi- 
tate. Dilute  with  equal  volume  of  water,  pass  hydro- 
gen sulphide  gas,  and  filter  off  precipitate,  Sb2S3,  on  a 
weighed  Gooch  crucible.  Wash  with  alcohol  and  car- 
bon bisulphide  to  remove  sulphur.  Dry  and  weigh. 

249.   ANALYSES  OF   LEADED  ZINCS   BY  THE   AUTHOR. 

I.  II.  in. 

Moisture 0.03  0.02  0.04 

Sulphur  dioxide 0.30  0.29  0.50 

Zinc  sulphate 0 . 86  1 . 49  1 . 26 

Lead  sulphate 26.46  19.76  23.06 

Zincoxide 72.11  78.11  74.72 

Undetermined 0.24  0.33  0.42 


100.00  100.00  100.00 

I.  II.  in.  IV. 

Moisture 0.29  0.58  0.20  0.26 

Sulphur  dioxide 0.01  0.01  0.01  0.01 

Arsenious  oxide 0.68  0.47  0.32  1.60 

Antimony  oxide 0 . 20  0 . 33  0 . 20  0 . 88 

Silica 0.14        0.05  0.04 

Zinc  sulphate 0.78  0.55  1.61  0.84 

Lead  sulphate 46.00  48.80  46.66  49.82 

Zincoxide 51.70  49.15  50.90  46.48 

Undetermined   .                                  0.20  0.11  0.05  0.07 


100.00       100.00       100.00       100.00 

250.  Moisture.    •  Analysis  of  lithopone,  ponolith,  etc. 
Heat  2  grams  at  105°  C.  for  3  hours.     Loss  in  weight 
represents  hygroscopic  moisture. 

251.  Barium  sulphate.     To  1  gram  add  10  c.c.  of  hy- 
drochloric acid  and  10  c.c.  of  water,  heat  gently  until 
excess  of  acid  has  been  expelled,  dilute  with  100  c.c.  of 
water,  and  boil  gently  for  10  minutes.     Filter,  ignite 
and  weigh  residue  as  barium  sulphate. 

252.  Total    zinc.    Neutralize    the    filtrate    from   the 
barium  sulphate  with  ammonia,  make  distinctly  acid 
with  hydrochloric  acid,  heat  to  about  80°  C.,  and  titrate 


SUBLIMED  WHITE  LEAD  AND  ZINC  PIGMENTS.      123 

with  standard  potassium  ferrocyanide  as  described  in 
Chapter.  XVI. 

253.  Zinc  sulphide.     Fuse  1  gram  in  a  larger  crucible 
with  a  mixture  of  potassium  nitrate  and  potassium 
chlorate  for  about  half  an  hour.      Dissolve  the  fused 
mass  in  dilute  hydrochloric  acid  and  boil  the  solution 
with  a  strong  nitric  acid  for  half  an  hour.     Filter  off 
the  insoluble  residue,   precipitate  the  combined  sul- 
phuric acid  in  the  filtrate  with  barium  chloride  in  the 
usual  manner,  filter,  ignite,  and  weigh. 

Wt.  barium  sulphate  X  0.1373  =  wt.  sulphur. 
Calculate  sulphur  to  zinc  sulphide. 

254.  Zinc  oxide.     Calculate  excess  of  zinc  over  what 
is  required  to  form  the  zinc  sulphide  to  zinc  oxide. 

255.  Calcium.     Occasionally  zinc  sulphide  whites  are 
found  on  the  market  in  which  the  barium  sulphate  has 
been  wholly  or  partially  replaced  with  calcium  sulphate. 
In  which  case  the  calcium  is  estimated  in  the  usual  man- 
ner, after  the  removal  of  the  zinc  as  sulphide,  and  the 
sulphuric  acid  combined  with  the  calcium  determined 
as  usual.     The  sulphuric  acid  due  to  the  calcium  must 
be  deducted  from  the  total  sulphuric  acid  obtained  by 
oxidation  before  calculating  to  zinc  sulphide. 

256.    ANALYSES  OF  ZINC  SULPHIDE  WHITES  BY  AUTHOR. 

I.  II. 

Lithopone.         Ponolith. 

Moisture 0.20  0.18 

Barium  sulphate 69.62  69.19 

Zinc  sulphide 28.05  28.07 

Zinc  oxide 1 . 55  2 . 27 

Undetermined   .  0.58  0.29 


100.00         100.00 


CHAPTER  XIV. 

DETERMINATION  OF  FINENESS,  COVERING  POWER  AND 
TINTING  STRENGTH   OF  PIGMENTS. 

257.  Determination  of  the  comparative  fineness  of  pig- 
ments.   The  comparative  fineness,  or  perhaps  better, 
the  rate  of  settling  of  pigments,  may  be  determined  by 
means  of  the  following  apparatus: 

A  is  an  ordinary  graduated  cylinder  holding  100  c.c. 

B  is  a  black  metal  shield  attached  to  the  block  D, 
which  half  surrounds  the  cylinder,  and  is  provided  with 
a  round  opening  T\  of  an  inch  in  diameter,  exactly 
opposite  the  25  c.c.  graduation. 

C  is  an  electric  light. 

258.  The  cylinder  is  filled  to  the  100  c.c.  mark  with 
87  degrees  gasoline;  2  grams  of  the  pigment  to  be  tested 
are  introduced,  the  cylinder  stoppered,  shaken  25  times 
with  a  uniform  motion,  and  the  stop  watch  started  with 
the  last  shake.     The  cylinder  is  placed  in  position  and 
the  time  noted  until  the  outlines  of  the  aperature  can 
be  plainly  observed.     This  gives  an  excellent  method 
of  determining  the  comparative  fineness  of  pigments  of 
the  same  type. 

259.  Comparison  of  paints  for  covering  power.     The 
following    method    described    by    G.    W.    Thompson, 
though   open  to   criticism,   furnishes  in   many  cases 
much  valuable  data: 

"Use  white  pine  boards,  30  inches  long  by  10  inches 
wide,  and  approximately  1  inch  thick.  Each  end  of 
the  board  is  provided  with  a  cleat  having  a  tongue 
fitting  into  a  groove  on  the  end  of  the  board  and 

124 


FINENESS,  COVERING  POWER,  TINTING  STRENGTH.     125 

securely  nailed  on.  The  entire  board,  including  the 
cleats,  to  be  finished  to  the  size  given  above.  Three 
of  these  boards  may  be  primed  with,  say,  the  follow- 
ing paint  mixture: 

White  lead  paste       100  Ibs. 

Linseed  oil,  —  |  boiled 75  Ibs. 

• 

No  attempt  is  made  to  secure  a  definite  amount  of 
priming  paint  to  the  unit  of  surface;  this,  for  the 


FIG.  6. 

reason  that  the  boards  may  vary  considerably  in  their 
absorptive  power.  When  this  priming  coat  is  dry, 
each  board  receives  a  diagonal  stripe  of  lampblack  in 
japan  about  1  inch  wide  on  one  or  both  sides  of  the 
board,  as  may  be  desired.  When  this  black  stripe  is 
dry  it  is  given  a  second  coat  of  paint  mixed  to  a  consis- 
tency proper  for  painting,  the  formula  being  recorded. 

260.  "The  weight  per  gallon  of  the  paint  so  mixed  is 
then  obtained  by  finding  its  specific  gravity  and  mul- 
tiplying by  8.33,  which  gives  the  weight  per  gallon. 


126  PAINT  AND  VARNISH  PRODUCTS. 

Inasmuch  as  the  board  used  has  a  total  surface  of  680 
square  inches,  all  that  is  required  to  be  done  is  to  find 
what  the  ratio  is  between  680  square  inches  and  the 
spreading  rate  at  which  it  is  desired  to  apply  the  paint 
in  order  to  find  the  fraction  of  the  gallon  to  be  applied 
to  each  board.  If  the  rate  adopted  is  120Q.  square  feet 
to  the  gallon,  then  we  get  the  formula: 

680  sq.  inches  :  1200  sq.  feet  :  :  1  .  .  x, 

the  reciprocal  of  V  being  the  fraction  of  a  gallon  of 
paint  to  be  applied  to  each  board,  one  coat.  Having 
the  weight  of  the  paint  per  gallon  we  easily  get  the 
amount  of  paint  by  weight  to  apply  to  each  board,  one 
coat  on  all  sides.  When  this  second  coat  of  paint  is 
thoroughly  dry,  a  similar  coat  is  applied;  and,  when 
dry,  the  boards  can  be  compared  for  the  covering 
power  of  the  paints  on  them.  We  mention  the  paint- 
ing of  three  boards  with  each  paint  to  be  compared. 
The  purpose  of  this  is  that  variations  in  results  are 
obtained  between  boards  which  are  apparently  painted 
in  an  identical  manner.  These  variations  are  not 
great,  but  it  is  thought  best  to  eliminate  them,  to  a 
certain  extent,  by  painting  three  boards  and  selecting 
the  one  giving  medium  results  for  comparison  with 
boards  painted  with  other  paints." 

261.  Determination   of   the   tinting   strength   of   colors. 
The  determination  of  the  tinting  strength  of  color  pig- 
ments is  a  very  necessary  operation  in  the  valuation 
and  use  of  color  pigments.     The  colors  should  always 
be  compared  with  a  carefully  selected  standard. 

262.  Chrome  yellows,  ochres  and  greens.     Weigh  out 
0.05  gram  of  color,  place  on  a  large  glass  plate,  add  12 
drops  of  bleached  linseed  oil,  and  rub  up  with  a  flat- 
bottomed  glass  pestle  or  muller,  then  add  1  gram  of 


FINENESS,  COVERING  POWER,  TINTING  STRENGTH.     127 

zinc  oxide,  kept  solely  for  this  purpose,  and  grind  with 
a  circular  motion  fifty  times,  gather  up  with  a  sharp- 
edged  spatula  and  grind  out  twice  more  in  like  manner, 
giving  the  pestle  a  uniform  pressure. 

Weigh  out  0.05  gram  of  the  color  kept  as  the  standard, 
and  treat  in  exactly  the  same  manner  as  described 
above.  Transfer  the  standard  to  a  microscope  slide 
and  spread  out  evenly,  drawing  the  spatula  in  one 
direction  only,  and  that  toward  the  end  of  the  slide. 
In  like  manner  transfer  the  prepared  sample  to  the 
slide,  spread  out  evenly  as  before,  drawing  the  spatula 
in  the  same  direction  as  directed  above,  and  bringing 
the  edge  of  sample  carefully  to  the  edge  of  the  stand- 
ard. Compare  the  tints  as  shown  on  both  sides  of  the 
glass. 

263.  Reds,  red  oxides,  etc.    Use  0.02  gram  of  sample 
to  one  gram  of  zinc  oxide. 

264.  Blues  and  blacks.    Use  0.01  gram  of  sample  to 
2  grams  of  zinc  oxide  with  24  drops  of  oil. 

265.  Paste  goods.    For  testing  the  strength  of  paste 
goods   a  can  containing  pure  zinc  oxide  ground  in 
bleached  linseed  oil  should  be  kept  on  hand. 

266.  Chrome  yellows,  ochres  and  greens.     Use  0.5  gram 
of  sample  to  10  grams  of  zinc  paste.     Weigh  accurately 
on  balanced  glasses  and  grind  as  described  above. 

267.  Reds,  red  oxides,  etc.    Use  0.2  gram  of  sample  to 
10  grams  of  zinc  oxide  paste. 

268.  Blues  and  blacks.    Use  0.05  gram  sample  to  10 
grams  of  zinc  oxide  paste. 


128 


PAINT  AND  VARNISH  PRODUCTS. 


209.   GRAVITY  AND  VOLUME  OF  PIGMENTS.1 


Name  of  Pigment. 

Sp.  Gr. 

Volume  Loose 
Pigment,  wt. 
per  gal.  in  Ibs. 

White  lead,  Dutch  Process      

6.750 

15.17 

Sublimed  lead 

6  396 

11  18 

Zinc  lead              

5  635 

6  64 

Lead  sulphate      

6  082 

9  77 

Zinc  oxide,  Green  Seal  

5.470 

3.57 

Zinc  oxide   selected 

5  554 

6  36 

Lithopone 

4  236 

8  80 

Barytes  domestic      

4  482 

16  96 

Barytes,  blanc  fix6     

4  329 

12.95 

Eng.  C.  S.  Paris  white  

2.705 

6.85 

Precipitated  chalk 

2  580 

2  82 

Terra  Alba  French 

2  358 

6  74 

Silica  floated      .       .    .           .       ... 

2  596 

6  47 

Silica   ground       

2  550 

4  40 

English  china  clay      

2  596 

3.83 

Talc 

2  749 

6  72 

Chrome  yellow  light 

6  413 

6  12 

Chrome  yellow  medium 

5  842 

6  57 

Chroma  yellow  deep     .    .       

5  910 

12  06 

Litharge,  yellow     

8  663 

32.21 

Litharge,  red   

8  781 

24.07 

Rochelle  ochre 

2  802 

5  61 

Red  lead  English 

8  681 

26  22 

Tuscan  red   dark 

3  660 

12  76 

Chrome  green,  light       

5  754 

11  51 

Chrome  green,  medium    

5  239 

13.05 

Prussian  blue    

1.956 

2.83 

Chinese  blue 

1  903 

3  85 

German  ivory  black 

2  619 

4  55 

Frankfort  black          .    .                      .... 

2  935 

6  17 

Bone  black    .       

2  319 

5  19 

Graphite    

2.293 

8.69 

Drugs,  Oils  and  Paints,  Vol.  XXI,  page  299. 


CHAPTER  XV. 

THE  PRACTICAL  TESTING   OUT   OF  PAINTS. 

270.  Paints  should  be  tested  out  by  the  chemist.    The 
chemical  analysis  of  a  can  of  paint  will  tell  much  re- 
garding the  value  of  that  paint,  but  a  thorough  prac- 
tical testing  out  on  a  suitable  surface  will  tell  more, 
and  the  two  in  conjunction  should  render  the  chemist's 
report  complete  and  above  question.     Often,  however, 
the  testing  out  is  done  by  a  so-called  " practical  man" 
who  has  little  or  no  knowledge  of  chemistry,  and  his 
report  for  that  very  reason  is  apt  to  be  misleading  to 
the  chemist.     In  order  to  secure  the  most  desirable 
results,  the  chemist  should  do  his  own  testing  out,  and 
this  involves  a  practical  painting  knowlege  that  can  be 
gained  only  by  experience  and  under  the  guidance  of 
an  able  master  painter. 

271.  Equipment.     The  chemist,  if  he  is  to  do  his  own 
testing   out,   should   provide   himself  with   an   ample 
equipment  so  that  he  may  carry  on  his  work  unham- 
pered.    He  should  have  mixing  cans  large  enough  to 
hold  sufficient  paint  for  the  coat  to  be  applied  and  to 
allow  stirring  without  danger  of  slopping  over  the  side. 
A  number  of  flat  paddles  of  suitable  sizes,  a  set  of 
measures  and  a  strainer,   are  also  essential  articles. 
All  paint  from  the  priming  to  the  finishing  coat  should 
be  strained,  as  it  assists  in  securing  a  more  uniform 
mixture  than   can  be  obtained  by  stirring.     This  is 
especially  necessary  where  tints  are  to  be  tried  out. 

272.  The  chemist  should  be  provided  with  a  good  set 
of  brushes.     It  is  a  serious  mistake  to  work  with  too 

129 


130  PAINT  AND  VARNISH  PRODUCTS. 

few  brushes.  For  ordinary  testing,  the  author  believes 
that  oval  brushes  should  be  used,  and  never  a  large  flat 
brush  which  simply  mops  the  paint  on  and  does  not 
assist  it  in  penetrating  into  the  fibres  of  the  wood. 
An  oval  brush,  being  necessarily  stiffer,  rubs  the  oil 
and  pigment  into  the  wood,  thoroughly  satisfying  it. 
For  trimming  and  finishing  the  edges,  a  good  chiseled 
varnish  brush  can  be  used  with  advantage.  Having 
provided  himself  with  a  good  set  of  brushes,  the  paint 
chemist  should  take  good  care  of  them.  New  brushes 
should  never  be  placed  in  water.  At  the  close  of  the 
day's  work  they  may  be  laid  out  full  of  paint  on  a 
board,  but  should  not  be  left  this  way  for  more  than 
twenty-four  hours.  When  through  with  the  brushes  for 
a  time,  they  should  be  laid  in  a  regular  paint  trough, 
containing  raw  oil,  or  they  may  be  suspended  in  a  can 
of  raw  oil  containing  a  little  turpentine,  to  prevent  the 
oil  from  becoming  fatty.  They  should  not  be  allowed 
to  stand  on  end,  as  it  turns  the  painting  edge  of  the 
brush.  Neither  should  brushes  be  allowed  to  remain 
for  long  intervals  in  cans  of  paint.  Brushes  should 
never  be  allowed  to  get  " lousy"  through  the  paint 
drying  on  the  bristles.  In  use,  the  brush  should  be 
handled  in  such  a  manner  as  to  wear  the  bristles  to  a 
chisel  edge-like  point,  and  should  never  be  jabbed  into 
corners,  but  carefully  worked  in. 

273.  The  requisites  for  a  paint.    The  requisites  for  a 
high-grade  paint  are : 

a.  Covering  power. 

6.  Spreading  capacity. 

c.  Durability. 

d.  Wearing  evenly. 

e.  Failing  by  gradual  wear,  and 

/.    Leaving  a  good  surface  for  repainting. 


THE  PRACTICAL  TESTING  OUT  OF  PAINTS.       131 

In  order  to  test  out  a  paint  to  determine  to  what  de- 
gree it  will  fulfill  the  above  requirements,  the  chemist 
must  have  a  clear  understanding  of  the  practical  appli- 
cation of  paint  and  the  suitability  of  different  surfaces 
to  receive  paint  of  varying  consistencies. 

274.  Relation  of  the  surface  to  the  paint.  The  surface 
on  which  the  paint  is  to  be  tested  out  is  of  prime  im- 
portance, as  it  vitally  affects  the  oil  and  turpentine 
reduction  which  should  be  given  the  paint.  If  the  sur- 
face is  a  dense  close-grained  wood,  a  much  more  liberal 
turpentine  reduction  must  be  used  than  when  the  sur- 
face is  more  porous,  as  in  the  case  of  soft  pine.  The 
lumber  used  should  be  well  seasoned  and  entirely  free 
from  dampness;  and  for  outside  paints,  the  surface 
should  be  exposed  to  the  direct  rays  of  the  sun  for  at 
least  a  couple  of  days  before  applying  the  paint,  even 
if  the  surface  is  apparently  free  from  moisture.  If  the 
test  is  to  be  applied  on  a  new  building,  every  precaution 
should  be  taken  that  the  lumber  has  dried  out  thor- 
oughly after  the  plastering  has  been  done.  It  must  be 
remembered  that  there  are  eighty  to  ninety  gallons  of 
water  in  every  hundred  square  yards  of  plaster,  and  if 
the  house  is  kept  closed  during  the  time  the  plaster  is 
drying,  the  moisture  must  pass  through  the  clapboard 
siding,  over  which  the  paint  is  to  be  spread,  in  order  to 
escape.  This  operation  is  much  slower  and  takes  a 
great  deal  longer  time  for  completion,  than  most  paint 
men  believe.  This  is  especially  true  if  the  house  is 
sheathed  with  one  or  more  thicknesses  of  paper  be- 
tween the  boarding  and  siding.  If  the  tests  are  to  be 
placed  on  small  test  frames,  such  as  are  described 
below,  or  on  specially  constructed  test  fences,  the  con- 
ditions affecting  the  application  of  the  paint  can  be 
more  easily  controlled. 


132  PAINT  AND  VARNISH  PRODUCTS. 

275.  Test    structures.   A    convenient,    practical,    and 
efficient  method  of  conducting  exposure  tests  is  shown 
in  the  illustration  at  the  beginning  of  this  book,  which 
represents  the  first  .of  a  series  of  tests  which  are  being 
conducted  by  the  North  Dakota  Government  Experi- 
ment Station. 

This  structure  is  75  feet  in  length,  6  feet  6  inches  high, 
begins  15  inches  from  the  ground,  and  faces  east  and 
west.  The  posts  are  5  feet  apart  and  bedded  in  con- 
crete. One  side  of  the  structure  is  plain  boarded,  the 
other  side  clapboarded,  the  top  capped,  and  the  ends 
boxed  in  a  suitable  manner.  Four  kinds  of  lumber 
were  used  in  the  construction,  representing  four  of  the 
most  common  varieties  used  for  house  building,  and 
were  securely  nailed  to  studding  set  1  foot  and  8  inches 
apart.  The  structure  was  divided  off  into  sections  16 
inches  wide  and  5  feet  in  length,  giving  sufficient  sur- 
face for  the  careful  brushing  out  of  the  paint ;  each  type 
of  paint  being  applied  over  the  four  kinds  of  wood,  and 
the  work  being  three  coats  in  each  case.  Twenty-one 
mixed  paints  and  white  leads  were  applied  on  this 
fence,  representing  prevailing  types  of  combinations. 

Figure  7  represents  a  second  series  of  exposure  tests 
begun  during  the  summer  of  1907.  These  fences  are 
like  the  one  described  above,  except  that  they  are  each 
100  feet  in  length.  There  is  a  four-inch  air  space  be- 
tween the  two  surfaces  of  each  fence,  the  numerous 
crevices  between  the  boards  permit  of  free  circulation 
of  air,  and  insure  the  prevention  of  continued  damp- 
ness on  the  inside  of  the  structure.  Figure  8  illustrates 
the  framework  to  which  the  boards  and  siding  were 
nailed. 

276.  A  more  convenient  method  for  making  exposure 
tests,    the   painting   of  which   may  be   done   in   the 


THE  PRACTICAL  TESTING  OUT   OF  PAINTS.       135 

laboratory,  is  illustrated  in  Fig.  9.  These  test  frames, 
so-called,  have  the  additional  merit  of  being  easily  trans- 
ported from  one  place  to  another  for  inspection.  These 
frames  are  3  feet  in  length  and  16  inches  in  width,  the 
edge  of  the  upper  clapboard  projecting  half  an  inch 
above  the  cleats,  arid  the  lower  clapboard  set  out  a 


FIG.  9.  —  PORTABLE  TEST  FRAMES. 

little,  so  that  two  or  more  frames  may  be  put  together, 
forming  a  unit  surface  exactly  similar  to  the  side  of 
a  house.  These  frames  are  made  to  be  screwed  to  a 
framework  like  that  illustrated  in  Fig.  8.  The  clap- 
boards, four  in  number,  are  set  four  inches  to  the 
weather  and  are  of  two  kinds  of  wood.  The  arrange- 
ment of  the  back  cleats  a,  a,  a  and  the  end  strips  b,  b 
through  which  the  screws  are  inserted  to  hold  the 


136  PAINT  AND  VARNISH  PRODUCTS. 

frame  to  the  skeleton  fence,  are  clearly  shown  in  the 
illustrations. 

These  end  strips  serve  a  much  more  important  pur- 
pose, and  one  which  makes  the  tests  much  more  valu- 
able than  on  a  plain  board  surface,  in  that  it  tests  out 
the  brushing  qualities  of  the  paint  very  thoroughly.  A 
poor  paint  will  often  brush  out  satisfactorily  on  an 
ordinary  flat  section  of  board,  but  will  at  once  show  its 
inferior  quality  when  the  painter  attempts  to  work  it 
into  the  corners  and  brush  it  away  from  the  end  strips, 
on  the  clapboard  surface.  In  fact,  it  closely  reproduces 
the  actual  conditions  which  the  painter  would  encounter 
in  applying  the  paint  on  an  average  house. 

277.  Application  of  the  priming  coat.      In  order  to  secure 
the  best  results  with  any  given  paint,  three  coats  should 
be  applied;  of  these  three  the  most  important  is  the 
priming  coat.     It  compares  with  the  foundation  of  a 
house,  which,  if  not  solidly  and  firmly  constructed,  ren- 
ders the  whole  superstructure  unstable.     The  priming 
coat,  if  not  bedded  thoroughly  in  the  wood,  will  not 
serve  to  anchor  and  firmly  bind  the  two  additional 
coats  to  the  surface.     The  essential  consideration  with 
the  priming  or  first  coat  is  to  secure  suitable  penetra- 
tion into  the  wood.     In  other  words,  the  wood  must  be 
thoroughly  satisfied.     The  necessity  of  this  is  explained 
with  great  force  and  clearness  by  J.  B.  Campbell,  in 
his  work  entitled  " Practical  Painting." 

278.  The  paint  to  be  tested  out,  if  of  the  ready  mixed 
type,  should  be  thoroughly  "  broken  up,"  first  pouring 
off  the  oil  portion,  stirring  the  residue  until  free  from 
lumps,  and  then  gradually  working  the  oil  portion  back 
into  the  paste.     This  is  best  accomplished  by  removing 
the  entire  contents  of  the  can  into  a  larger  mixing  can, 
kept  solely  for  this  purpose.     The  consistency  of  the 


THE  PRACTICAL  TESTING  OUT  OF  PAINTS.       137 

paint  after  being  "  broken  up  "  should  be  carefully  noted, 
whether  it  is  thin,  medium,  or  heavy,  as  the  amount  of 
reduction  which  the  paint  will  stand  depends  largely  on 
its  consistency. 

279.  Raw  linseed  oil  should  almost  without  exception 
be  used  instead  of  boiled  oil  for  reducing  the  paint  for 
the  priming  coat.     Raw  oil  dries  slowly  and  from  the 
bottom  up,  which  allows  it  to  be  thoroughly  absorbed 
and  to  harden  uniformly.     Boiled  oil  does  not  penetrate 
the  wood,  owing  to  its  rapid  drying  qualities,  and  hence 
the  coating  formed  is  a  surface  coating  only,  and  does 
not  become  firmly  anchored  to  the  wood.     Turpentine 
should  be  used  liberally  in  the  priming  coat,  as,  by  re- 
ducing the  specific  gravity  and  rendering  the  oil  more 
mobile,   it  assists   it   in  penetrating  into  the  deeper 
pores  of  the  wood,  thus  securing  increased  penetration 
and  also  more  rapid  drying.     The  harder  and  closer 
grained  the  wood,  the  larger  the  amount  of  turpentine 
required. 

280.  The  following  oil  and  turpentine  reductions 1  will 
enable  the  chemist  to  judge  the  reduction  required  in 
most  cases. 

281.  Oil  reductions.     "  A  full  oil  reduction  consists  of 
oil  only,  with  the  exception  of  7V  gallon  of  turpentine 
to  the  gallon  of  paint,  to  assist  in  penetration;  this  is  not 
enough  turpentine  to  destroy  the  luster  of  the  paint, 
and  will  accomplish  the  purpose  of  penetrating  a  hard 
or  glossy  surface  where  it  would  be  unsatisfactory  -to 
apply  paint  without  the  addition  of  a  small  percentage 
of  this  thinner." 

282.  "A  liberal  oil  reduction  consists  of  seven  eighth 
oil  and  one  eighth  turpentine  to  form  the  total  amount 
of  reducers;  this  amount  of  turpentine  will  cause  more 

1  Campbell,  Practical  Painting,  p.  63. 


138  PAINT  AND  VARNISH  PRODUCTS. 

rapid  and  even  penetration,  but  will  not  destroy  the 
luster  of  heavy-bodied  paint." 

283.  "A    medium    oil   reduction    consists   of   three 
fourths  oil  and  one  fourth  turpentine  to  form  the  total 
amount  of  reducers;  this  amount  of  turpentine   will 
destroy  part  of  the  luster  and  cause  deep  penetration 
on  a  hard  surface." 

284.  Turpentine  reductions.     "  A  full  turpentine  reduc- 
tion consists  of  nothing  but  turpentine,  and  is  used  for 
producing  a  flat  paint." 

285.  "A  liberal  turpentine  reduction  consists  of  seven 
eighths  turpentine  and  one  eighth  oil,  to  form  the  total 
amount  of  reducers." 

286.  "A  medium  turpentine  reduction  is  half  tur- 
pentine and  half  oil." 

287.  "Dark  shades  require  more  turpentine  to  pro- 
duce the  same  results,  as  to  penetration  and  flattening 
the  paint,  than  light  shades.     Zinc  and  combination 
paints  require  more  turpentine  than  strictly  pure  lead  to 
produce  the  same  results,  as  to  destroying  the  luster  of 
the  paint.     Where  light  shades  require  f  gallon  of  tur- 
pentine to  produce  the  desired  results  as  to  flattening 
or  destroying  the  luster  and  securing  penetration,  dark 
shades  require  T\  of  a  gallon  to  produce  like  results." 

288.  It  is  also  well  to  remember  in  making  the  reduc- 
tion that  turpentine  reduces  twice  as  fast  as  raw  oil. 
The  consistency  to  which  the  paint  should  be  reduced 
for  priming  must  necessarily  be  left  to  the  judgment  of 
the  person  applying  it,  and  hence  no  definite  directions 
can  be  given,  but  the  following  directions  given  by 
Campbell1  have  been  found  very  helpful  by  the  author. 

289.  "In  priming  soft  wood,  the  paint  should  be  ap- 
plied with  a  full  brush,  and  enough  paint  used  at  all 

1  Practical  Painting,  p.  69. 


THE   PRACTICAL  TESTING  OUT   OF  PAINTS.       139 

times  to  satisfy  the  surface.  It  should  be  well  brushed, 
and  especially  on  the  harder  grain,  to  assist  or  force  the 
paint  into  this  close  grain,  and  remove  by  hard  brush- 
ing any  surplus  paint  that  remains  on  the  surface.  On 
hard  or  close-grained  wood  a  medium  full  brush  should 
be  used  in  applying  the  paint,  as  this  class  of  wood 
does  not  possess  the  absorbing  properties  of  softer 
woods,  but  requires  more  brushing  in  order  to  force  a 
sufficient  amount  of  oil  and  binder  into  the  wood  and 
at  the  same  time  not  leave  an  excess  of  paint  on  the 
surface." 

290.  "If  the  priming  coat  is  of  the  proper  consistency, 
carrying  sufficient  pigment  to  fill  and  hide  the  grain,  and 
well  brushed  into  the  wood,  most  of  the  absorption  will 
have  ceased  with  this  coat  and  no  excess  of  pigment  be 
left  on  the  surface.     This  thin  coat  will  allow  the  second 
coat  to  penetrate  through  and  satisfy  any  part  of  the 
wood  which  was  not  fully  filled  at  the  time  of  priming, 
and  also  allow  the  second  coat  to  bind  itself  to  the  wood 
and  priming  coat." 

291.  Application  of  the  middle  coat.    The  priming  coat 
should  be  given  ample  time  to  dry  before  applying  the 
second  coat,  which,  as  Mr.  Campbell  states  with  much 
truth,  should  be  "considered  the  medium  between  the 
foundation  coat  and  the  protecting  or  finishing  coat." 
Careful  judgment  should  be  exercised  in  preparing  the 
paint  for  this  coating.     "It  must  not  be  too  elastic,  and 
should  dry  firm  without  a  high  gloss.     Too  heavy  an  oil 
reduction  will  leave  a  high,  glossy  surface,  over  which 
the  finishing  coat  will  not  adhere  or  properly  dry." 
Sufficient  turpentine  should  be  used  to  secure  the  nec- 
essary penetration  into  the  priming  coat  and  to  "flat- 
ten" out  the  paint  so  that  it  will  show  little  or  no  gloss 
after  48  to  72  hours.     Over  such  a  surface  the  finishing 


140  PAINT  AND  VARNISH  PRODUCTS. 

coat  can  be  applied  evenly,  smoothly,  and  with  great 
adherence.  The  directions  for  application  as  issued 
by  most  paint  manufacturers  are  apt  to  fall  short  in 
the  amount  of  turpentine  necessary  for  the  proper 
application  of  the  second  coat. 

292.  Nail  holes  and  cracks  should  be  carefully  put- 
tied.    Cheap  putty  should  be  avoided,  as  it  is  apt  to 
turn  yellow  and  ultimately  crumble  and  fall  out.     It 
is  often  better  for  the  paint  chemist  to  make  his  own 
putty,  using  medium  whiting,  raw  oil,  and  paste  white 
lead  to  about  20  per  cent  of  the  whiting  used.     The 
mixture  should  be  carefully  kneaded  and  worked  until 
of  stiff  consistency. 

293.  If  the  work  is  to  be  only  two-coat,  the  paint 
should  have  a  full  oil  reduction,  so  as  to  insure  suffi- 
cient elasticity  and  opacity,  and  should  be  worked  out 
well  under  the  brush. 

294.  Application    of   third    coat.    The   paint   for  this 
coat  should  be  of  good  consistency,  with  a  full  raw-oil 
reduction,  so  that  it  may  be  brushed  out  smoothly  and 
evenly,  and  be  sufficiently  elastic  so  as  to  withstand 
severe  exposures.     Too  much  importance  cannot  be 
placed  on  the  thorough  brushing  of  the  paint,  as  the 
durability  and  protection  it  affords  are  dependent  to  a 
great  extent  upon  the  thoroughness  with  which  this  is 
done.     Paint  flowed  on  will  soon  crack  and  come  off, 
while,  if  plenty  of  muscle  is  used,  it  will  make  the  finish- 
ing coat  adhere  more  firmly  to  the  second  coat. 

295.  Application  of  paste  leads  and   paste   paints.     In 
testing  out  paste  paints  and  leads  some  convenient 
method  should  be  adopted  for  calculating  the  amount 
of  oil  used  in  gallons  per  hundred  pounds  of  paste.     One 
of  the  simplest  schemes  is  to  weigh  out  the  leads  or 
pastes  in  12|  oz.  quantities  or  multiples  thereof.     Then 


THE  PRACTICAL  TESTING  OUT  OF  PAINTS.       141 

each  ounce  of  oil  used  is  equivalent  to  one  gallon  per 
hundred  pounds  of  paste. 

One  gallon  is  equivalent  to  128  oz. 

One  hundred  pounds  are  equivalent  to  1600  oz. 

1600  -5-  128  =  12.5 

In  this  way  the  necessary  quantities  of  turpentine  and 
drier  can  be  rapidly  calculated  and  measured  out.  For 
instance,  if  a  specification  to  be  tested  out  read, 

100  Ibs.  white  lead, 
7  gal.  raw  linseed  oil, 
\  gal.  turpentine, 
|  gal.  turpentine  drier, 

the  above  scheme  would  call  for 

12 J  oz.  White  lead, 
7  oz.  raw  linseed  oil, 
\  oz.  turpentine, 
\  oz.  turpentine  drier. 

If  larger  amounts  were  required,  the  necessary  mul- 
tiple of  12|  should  be  used  and  the  other  figures  in- 
creased accordingly. 

296.  Driers.  The  proper  use  of  driers  is  often  a  per- 
plexing problem  with  the  paint  chemist.  Campbell l 
says:  "A  wide  experience  with  the  products  as  used  by 
the  painter  shows  the  greatest  possible  difference  be- 
.tween  them.  Some  of  them  are  sufficiently  powerful 
so  that  even  5  per  cent  added  to  raw  oil  is  enough  to 
cause  it  to  dry  as  fast  as  with  boiled  oil,  and  not  only 
that,  but  to  dry  throughout  or  from  the  bottom  up,  and 
not  merely  surface  dry,  as  will  boiled  oil.  Others  again 
are  so  loaded  with  rosin  and  petroleum  products  and 
so  deficient  in  true  drying  properties  that  25  per  cent  or 

1  Practical  Painting,  p.  66. 


142  PAINT  AND  VARNISH  PRODUCTS. 

more  is  required  to  accomplish  this  result,  and  then  the 
resulting  surface  will  be  spongy  or  brittle,  as  the  case 
may  be,  but  in  any  event  lacking  in  durability."  In 
the  face  of  these  conditions  the  only  recourse  left  the 
chemist  is  to  test  out  his  driers  thoroughly,  as  described 
in  a  later  chapter." 

297.  "The  Japan  or  drier  should  be  mixed  with  the 
paint  while  it  is  in  semipaste  form.  The  mixing  is 
thus  uniform  and  the  results  satisfactory.  If  an  at- 
tempt is  made  to  add  it  after  the  paint  is  ready  for  the 
brush,  the  Japan  is  liable  to  curdle;  it  will  be  difficult 
to  mix  uniformly  and  the  resulting  work  is  liable  to  be 
spotted,  drying  flat  in  some  places  and  glossy  in  others." 
It  should  be  borne  in  mind  that  paints  containing  zinc 
or  dark  colors  will  require  more  Japan  than  white  lead 
alone,  provided  that  it  is  essential  to  dry  in  a  given 
time. 


CHAPTER  XVI. 

ANALYSIS   OF  WHITE  PAINTS. 

298.  Qualitative  analysis.    In  the  majority  of  cases  a 
complete  qualitative  analysis  of  the  pigments  present 
is  hardly  worth  the  time  it  requires,  as  there  is  but 
little  time  lost  in  following  the  regular  quantitative 
scheme.     If,  however,  a  qualitative  analysis  is  desired, 
the  following  outline  will  be  found  sufficient  in  most 
instances,  the  removal  of  the  vehicle  previous  to  these 
tests  being  understood. 

299.  Carbonates.     Effervescence    with    concentrated 
hydrochloric  acid  indicates  carbonates,   or   hydrogen 
sulphide  if  zinc  sulphide  be  present,  the  latter  being 
distinguished  by  its  odor  and  by  the  fumes  blackening 
a  piece  of  filter  paper  moistened  with  lead  acetate. 

300.  Barytes,  silica,  clay,  or  other  silicates.     Boil  above 
mixture  five  minutes,  dilute  with  boiling  water,  filter. 
An  insoluble  residue  may  be  barytes,  silica,  clay,  or 
other  silicates.     Test  for  barytes  with  flame  test,  using 
a  platinum  wire.     A  characteristic  green  color  indicates 
barium. 

301.  Sulphates.    Test  a  small  portion  of  the  acid  fil- 
trate for  combined  sulphuric  acid  with  a  few  drops  of 
barium  chloride. 

302.  Lead.     Test  another  small  portion  of  the  acid  fil- 
trate with  sulphuric  acid.     A  white  precipitate  at  once, 
or  on  standing  indicates  lead. 

303.  Zinc.     Take  another  small  portion  of  the  acid  fil- 
trate and  add  a  few  drops  of  potassium  ferrocyanide. 
A  white  precipitate  with  a  bluish  tinge  indicates  zinc. 

143 


144  PAINT  AND  VARNISH  PRODUCTS. 

304.  Calcium.     The  remaining  portion  of  the  acid  ni- 
trate is  made  alkaline  with  ammonia  and  hydrogen  sul- 
phide passed  in  for  five  minutes.     Filter  and  test  filtrate 
for  calcium  with  ammonium  oxalate,  setting  aside  in  a 
warm  place. 

305.  Magnesium.     After  completely  precipitating  the 
calcium  add  a  few  drops  of  hydrogen  sodium  phosphate. 
A  precipitate  on  standing  indicates  the  presence  of  mag- 
nesium compounds. 

The  identification  of  the  forms  in  which  the  lead 
may  occur  can  only  be  determined  by  the  quantitative 
scheme  if  both  sulphates  and  carbonates  are  present. 

Quantitative  Analysis  of  White  Paints. 

306.  Total  lead.     Weigh  1  gram  of  the  dry  pigment  into 
a  250  c.c.  beaker.     Add  30  c.c.  of  strong  hydrochloric 
acid,  boil  5  minutes,  add  50  c.c.  of  hot  water,  heat  15 
minutes  longer,  settle,  filter  while  hot,  and  wash  thor- 
oughly with  boiling  water.     The  washing  should  be 
begun  the  instant  the  solution  has  filtered  through,  in 
order  to  avoid  any  crystallization  of  lead  chloride  in 
the  pores  of  the  filter  paper.     Once  formed  the  crystals 
can  only  be  dissolved  with  difficulty  and  with  the  use 
of  an  excess  of  wash  water,  which,  as  stated,  must  be 
at  boiling  temperature.  -  This  operation  is  best  con- 
ducted by  the  aid  of  suction.     Casein  and  other  prod- 
ucts of  a  similar  nature  are  occasionally  used  in  the 
manufacture  of  mixed  paints  in  considerable  quantities, 
and  the  analyst  should  always  be  on  the  lookout  for 
the  possible  presence  of  these  substances. 

307.  The  solution  is  made  just  alkaline  with  ammo- 
nia, then  just  acid  to  litmus  with  hydrochloric  acid.     It 
is  very  necessary  that  the  solution  be  only  barely  acid, 


ANALYSIS  OF  WHITE  PAINTS.  145 

as  a  comparatively  small  quantity  of  free  acid  will  keep 
considerable  lead  from  precipitating.  Having  been" 
made  barely  alkaline,  which  is  indicated  by  the  precip- 
itation of  the  lead,  the  solution  is  brought  to  a  faintly 
acid  condition  by  using  dilute  hydrochloric  acid  (1  to 
10).  Dilute  to  about  350  c.c.  Cool,  pass  in  hydrogen 
sulphide  gas,  noting  the  color  of  the  precipitate :  if  gray, 
some  zinc  is  being  thrown  down;  if  reddish  black,  the 
solution  is  too  acid.  Add  a  few  drops  of  dilute  acid 
or  ammonia  as  the  case  requires.  Settle,  filter,  and 
wash  with  cold  water. 

308.  Place  filter  and  precipitate  in  25  c.c.  of  nitric 
acid  and  25  c.c.  of  water,  heat  gently  until  the  lead  has 
all  dissolved,  as  shown  by  the  residual  sulphur  having  a 
yellow  to  whitish  color.     Do  not  boil  hard  enough  thor- 
oughly to  disintegrate  the  filter  paper.     If  difficulty  is 
experienced  in  dissolving  the  lead  contained  in  the  sul- 
phur particles,  it  is  better  to  collect  them  into  a  ball 
with  the  aid  of  a  stirring  rod  and  remove  to  a  small 
beaker  and  treat  with  a  few  cubic  centimeters  concen- 
trated nitric  acid,  and  heat  until  dissolved,  then  pour 
back  into  the  larger  beaker. 

309.  Pour  solution  and  filter  paper  on  to  a  suction 
funnel  provided  with  a  platinum  cone.     If  any  fine 
particles  pass  through,  pour  the  filtrate  back  again. 
This  procedure  permits  the  washing  of  the  filter  mass 
with  a  very  small  amount  of  water,  thus  saving  consid- 
erable time  in  the  subsequent  evaporation.    Add  5  c.c. 
of  dilute  sulphuric  acid  to  filtrate,  and  evaporate  until 
sulphur  trioxide  fumes  appear.     Cool,  add  25  c.c.  of 
water,  25  c.c.  of  alcohol;  allow  to  stand  one-half  hour 
with  occasional  stirring;  filter,  using  Gooch  crucible, 
wash  with  dilute  alcohol,  dry,  heat  gently  over  ordi- 
nary lamp,  and  weigh  as  lead  sulphate. 


146  PAINT  AND  VARNISH  PRODUCTS. 

310.  Calcium.    The  filtrate  containing  the  zinc,  cal- 
cium, and  possibly  magnesium  is  made  slightly  alkaline 
with  ammonia,  a  few  drops  of  a  mercuric  chloride  solu- 
tion (1  to  10)  added,  and  a  stream  of  hydrogen  sulphide 
gas  passed  into  the  solution  for  about  ten  minutes. 

The  addition  of  the  mercuric  chloride  renders  the 
precipitate  granular  and  very  easy  to  filter,  and  en- 
tirely obviates  the  difficulty  of  filtering  a  slimy  zinc 
sulphide  precipitate.  In  the  analysis  of  tints  where  the 
zinc  cannot  be  titrated  until  it  has  been  freed  from  iron, 
the  addition  of  the  mercuric  chloride  will  not  cause  any 
trouble,  as  treatment  with  hydrochloric  acid  results  in 
the  solution  of  the  zinc  only,  the  mercuric  sulphide 
being  insoluble  in  hydrochloric  acid.  Settle,  decant, 
filter,  and  wash. 

311.  Evaporate  the  filtrate  from  above  precipitate  to 
about  150  c.c.,  make  alkaline  with  ammonia,  add  ammo- 
nium oxalate  (50  c.c.  for  1  gram  of  lime),  usually  20  c.c. 
is  sufficient,  and  set  in  a  warm  place  for  two  or  three 
hours.     Filter,  wash,  ignite,  and  weigh  as  calcium  oxide, 
or  titrate  precipitate  with  permanganate  by  placing 
filter  and  the  thoroughly  washed  precipitate  in  a  400 
c.c.  beaker,  adding  200  c.c.  of  boiling  water  and  25  c.c. 
of  dilute  sulphuric  acid,   and  titrate  with  standard 
tenth-normal  potassium  permanganate. 

1  c.c.  tenth-normal  permanganate  =  0.0028  gram  CaO. 
1  c.c.  tenth-normal  permanganate  =0.0050  gram  CaC03. 

Barium  carbonate  is  still  to  be  found  in  certain  mixed 
paints,  and  it  is  advisable  to  test  for  the  presence  of 
soluble  barium  with  a  few  drops  of  sulphuric  acid 
before  precipitating  the  calcium. 

312.  Magnesium.     The  filtrate  from  the  cajcium  oxa- 
late should  be  tested  for  magnesium  by  treating  with 


ANALYSIS  OF  WHITE  PAINTS.  147 

hydrogen  sodium  phosphate.  Allow  to  stand  one-half 
hour,  add  25  c.c.  of  ammonia,  allow  to  stand  one  hour, 
then  filter  on  to  a  Gooch  crucible,  wash  with  dilute  am- 
monia, ignite,  and  weigh. 

Weight    precipitate  X  0.7575  =  weight    magnesium 
carbonate. 

313.  Zinc  oxide.      Reagents.     Standard   zinc   solution. 
Dissolve  10  grams  of  chemically  pure  zinc  in  hydro- 
chloric acid  in  a  graduated  liter  flask,  add  50  grams  of 
ammonium  chloride,  and  make  up  to  1  liter. 

1  c.c.  =  0.01  gram  zinc  or  0.01245  gram  zinc  oxide. 

314.  Standard   potassium  ferrocyanide   solution.     Dis- 
solve 46  to  48  grams  of  crystallized  potassium  ferro- 
cyanide in  water,  make  to  1000  c.c. 

315.  Uranium  nitrate  solution.     Dissolve  15  grams  of 
uranium  nitrate  in  100  c.c.  of  water. 

316.  Standardizing  the  ferrocyanide  solution.    To  de- 
termine the  value  of  the  potassium  ferrocyanide  solu- 
tion, pipette  25  c.c.  of  the  zinc  solution  into  a  400  c.c. 
beaker.     Dilute  somewhat  and  make  faintly  alkaline 
with  ammonia,  bring  to  a  faintly  acid  condition  with 
hydrochloric  acid,  and  then  add  3  c.c.  excess  of  the  con- 
centrated acid,  dilute  to  a  total  volume  of  about  250  c.c., 
heat  to  80°  C.,  and  titrate  as  follows:  Pour  off  about  10 
c.c.  of  the  zinc  solution  into  a  small  beaker  and  set 
aside,  run  the  ferrocyanide  into  the  remainder  from  a 
'burette,  a  few  cubic  centimeters  at  a  time,  until  the 
solution  takes  on  a  slight  ash-gray  color,  or  until  a  drop 
of  the  solution  placed  in  contact  with  a  drop  of  the 
uranium  nitrate  solution  on  a  porcelain  plate  turns  to  a 
distinct  brownish  color.     Often  the  end  point  has  been 
passed  by  quite  a  little. 

317.  The  10  c.c.  of  zinc  solution  that  has  been  re- 
served is  now  added  and  the  titration  continued,  drop 


148  PAINT  AND  VARNISH  PRODUCTS. 

by  drop,  testing  a  drop  of  the  solution  carefully  on  the 
porcelain  plate  after  each  addition  of  ferrocyanide  solu- 
tion. Some  little  time  is  required  for  the  test  drop  to 
change  color,  so  that  the  end  point  may  have  been 
passed  slightly.  This  may  be  corrected  for  by  making 
a  memorandum  of  the  burette  readings,  having  the 
test  drops  arranged  in  regular  order  and  taking  as  the 
proper  reading  the  one  first  showing  a  distinct  brown- 
ish tinge.  Having  noted  the  number  of  cubic  centi- 
meters of  ferrocyanide  required  for  the  titration  of  the 
standard  zinc  solution,  the  value  of  1  c.c.  may  be  readily 
calculated. 

318.  Titration  of  sample.   One-half  gram  of  the  sample, 
if  high  in  zinc,  or  1  gram,  if  the  zinc  content  is  fairly  low, 
or  the  zinc  sulphide  precipitate  obtained  in  section  310, 
is  dissolved  in  a  covered  beaker  in  10  c.c.  of  hydrochlo- 
ric acid  and  10  c.c.  of  water,  the  solution  diluted  and 
treated  exactly  as  described  above  for  the  standard  zinc 
solution,  care  being  taken  to  titrate  to  exactly  the  same 
depth  of  color  on  the  porcelain  test  plate.    If  the  method 
is  carefully  carried  out,  the  procedure  being  uniformly 
the  same  in  each  determination,  the  results  will  be 
found  satisfactorily  accurate. 

319.  Lead  sulphate.   Dissolve  0.5  gram  in  water,  25  c.c. 
hydrochloric  acid  in  light  excess.     Dilute  to  200  c.c. 
and  add  a  piece  of  aluminum  foil  which  about  covers 
the  bottom  of  the  beaker.     It  is  important  that  this  be 
held  at  the  bottom  by  a  glass  rod.     Boil  gently  until 
the  lead  is  precipitated.     Completion  of  this  is  shown 
by  the  lead  ceasing  to  coat  or  cling  to  the  aluminum. 
Decant  through  a  filter,  pressing  the  lead  sponge  into 
a  cake  to  free  it  from  solution.     Add  to  filtrate  a  little 
sulphur-free  bromine  water,  ignite,  and  weigh  as  ba- 
rium sulphate.     Calculate  to  lead  sulphate  by  multi- 


ANALYSIS  OF  WHITE  PAINTS.  149 

plying  by  1.3  as  a  factor,  unless  calcium  sulphate  is 
present,  in  which  case  it  is  advisable  to  make  use  of 
Thompson's  separation. 

320.  In  the  absence  of  barium  sulphate  the  com- 
bined sulphuric  acid  may  be  estimated  by  H.  Mann- 
hard  t's  method :  Grind  1  gram  of  pigment  with  1  gram 
of   sodium    carbonate   very   intimately   in    an   agate 
mortar.     Boil  gently  for  ten  minutes,  the  combined 
sulphuric  acid,  and  in  the  case  of  colors  containing 
chro mates  the  chromic  acid,  will  pass  into  solution  and 
may  be  estimated  in  the  filtrate  in  the  usual  manner. 
If  necessary  collect  the  insoluble  portion  on  a  filter, 
dry,  detach,  and  triturate  a  second  time. 

321.  Basic  carbonate  of  lead  (white  lead).     After  de- 
ducting the  amount  of  lead  present  in  the  pigment  as 
sulphate  of  lead,  calculate  the  rest  of  the  lead  as  white 
lead  by  multiplying  the  remaining  sulphate  by  0.852, 
unless  sublimed  lead  is  suspected  to  be  present,  in 
which  case  the  combined  lead  oxide  must  be  taken  into 
consideration. 

322.  Insoluble   residue.     The  insoluble  residue  from 
the  original  hydrochloric  acid  treatment  may  contain 
barytes,  magnesium  silicate,  silica,  and  clay.     Ignite 
filter  paper  and  residue  until  white,  weigh  as  total  in- 
soluble matter;  grind  in  agate  mortar  with  about  10 
times  its  weight  of  sodium  carbonate,  fuse  for  1  hour 
in  a  platinum  crucible,  and  dissolve  out  in  hot  water. 

323.  Barium  sulphate.     The  solution  from  the  fusion 
is  filtered.     The  residue  consists  of  barium  carbonate, 
magnesium  carbonate,  etc.,  and  is  washed  with  hot 
water.     The  filtrate  and  washings  are  saved.     Pierce 
filter  paper  and  wash  precipitate  into  clean  beaker  with 
hot  dilute  hydrochloric  acid;  finish  washing  with  hot 
water,  heat  to  boiling,  add  10  c.c.  of  dilute  sulphuric 


150  PAINT  AND  VARNISH  PRODUCTS. 

acid  to  precipitate  barium,  filter,  ignite,  and  weigh  as 
barium  sulphate. 

324.  Silica.     The  filtrate  from  the  barium  sulphate  is 
added  with  care  to  the  filtrate  reserved  in  the  preceding 
paragraph,  making  distinctly  acid;  evaporate  to  com- 
plete dryness,  cool,  add  15  c.c.  of  hydrochloric  acid, 
heat  to  boiling,  cool,  settle,  filter,  ignite,  and  weigh  as 
silica. 

325.  Alumina.     The  filtrate  from  the  silica  will  con- 
tain all  of  the  alumina  except  that  which  was  dissolved 
in  the  original  treatment  with  hydrochloric  acid.     This 
is  quite  constant,  varying  from  .004  to  .005  gram  per 
gram  of  clay.     The  acid  filtrates  are  made  slightly  alka- 
line with  ammonia,   and  boil  until  odor  disappears. 
Settle,  filter,  wash,  ignite,  and  weigh  as  alumina. 

Weight  alumina  X  2.5372  =  weight  clay. 
Weight  clay  X  .4667  =  weight  of  silica  in  clay. 
Any  difference  greater  than  5  per  cent  may  be  con- 
sidered as  free  or  added  silica,  according  to  Scott. 

326.  Calcium  and  Magnesium  oxides.     If   qualitative 
test  shows  presence  of  magnesium  in  insoluble  residue 
from  the  first  hydrochloric  acid  treatment  it  was  present 
probably  as  magnesium  silicate.     Treat  filtrate  from  the 
aluminum  hydroxide  for  calcium  and  magnesium  oxides. 
Magnesium  silicate  contains  3  to  5  per  cent  combined 
water. 

327.  Hydrofluoric  acid  treatment.     Instead  of  resorting 
to  fusion  with  sodium  carbonate,  the  insoluble  residue, 
which  should  be  weighed  up  in  a  clean  platinum  crucible, 
may  be  treated  with  several  drops  of  pure  concen- 
trated hydrofluoric  acid  and  sulphuric  acid  and  heated 
gently  on  a  sand  bath  under   the  hood,  using  only 
sufficient  heat  slowly  to  volatilize  the  silica  and  sul- 
phuric acid.      Dissolve  out  in  water  acidulated  with 


ANALYSIS  OF  WHITE  PAINTS.  151 

hydrochloric  acid.  The  residue,  which  is  barium  sul- 
phate, is  filtered  off  and  estimated  as  such.  The  filtrate 
will  contain  a,ny  aluminum,  calcium,  and  magnesium 
present  which  may  be  estimated  and  calculated  as 
oxides  as  above  described.  The  combined  weight  of 
the  barium  sulphate,  alumina,  calcium,  and  magnesium 
oxides  subtracted  from  the  weight  of  the  insoluble 
residue  used  gives  the  weight  of  silica.  This  operation 
is  much  shorter  than  resorting  to  a  fusion  and  equally 
as  accurate. 

328.  Mixed   carbonates   and   sulphates.     Occasionally 
paints  are  met  with  which  contain  calcium  sulphate, 
calcium  carbonate,  sulphate  of  lead,  and  white  lead 
(basic  carbonate  of  lead),  in  which  case  it  is  necessary 
to  make  a  separation  of  the  calcium  compounds,  which 
may  be  effected  by  Thompson's  method  as  follows: 

To  1  gram  of  the  sample  are  added  20  c.c.  of  a  mix- 
ture of  nine  parts  alcohol  (95  per  cent)  and  one  part  of 
concentrated  nitric  acid.  Stir,  and  allow  to  stand  20 
minutes.  Decant  on  a  filter  and  repeat  the  treatment 
with  the  acid-alcohol  mixture  four  times,  allowing  it  to 
stand  each  time  before  decanting.  The  calcium  car- 
bonate will  go  into  solution,  while  the  calcium  sulphate 
or  gypsum  remains  undissolved.  Add  filter  and  con- 
tents to  the  residue  remaining  in  the  beaker;  dissolve  in 
hydrochloric  acid  with  sufficient  water  to  insure  the 
solution  of  the  calcium.  Make  alkaline  with  ammonia, 
pass  in  hydrogen  sulphide  for  10  minutes,  boil,  settle, 
filter.  The  filtrate  and  washings  are  concentrated  to 
about  150  c.c.  and  the  calcium  precipitated  with  am- 
monium oxalate  in  the  usual  manner.  The  ignited 
precipitate  is  calculated  to  hydrated  calcium  sulphate. 

329.  Estimation  of  carbon  dioxide  in  the  presence  of 
zinc  sulphide.     This  method,  devised  by  Mannhardt,  is 


152  PAINT  AND  VARNISH  PRODUCTS. 

often  useful  in  determining  complex  mixtures  of  pig- 
ments. One  gram  of  the  pigment  is  ground  for  several 
minutes  in  a  smooth  glass  mortar  with  an  excess  of 
bichromate  of  potash,  using  considerable  pressure;  the 
mixture  is  then  placed  in  the  carbon  dioxide  generator 
and  the  carbon  dioxide  liberated  and  estimated  in  the 
usual  manner. 

330.  Calculations.  The  ignited  precipitate  of  calcium 
oxide  obtained  from  the  portion  insolable  in  the  acid- 
alcohol  mixture  is  subtracted  from  the  total  calcium 
weighed  as  oxide ;  the  remaining  calcium  oxide  is  calcu- 
lated to  calcium  carbonate.  The  total  carbon  dioxide 
is  determined  in  a  portion  of  the  sample,  the  portion 
due  to  the  calcium  carbonate  is  deducted  from  the  total 
amount,  and  the  remainder  calculated  to  basic  carbon- 
ate of  lead.  The  combined  sulphuric  acid  due  to  the 
sulphate  of  lime  is  deducted  from  the  total  combined 
sulphuric  acid,  and  the  remainder  calculated  to  sulphate 
of  lead. 

Wt.  calcium  oxide  X  3.0715  =  hydrated  calcium  sul- 
phate. 

Wt.  calcium  oxide  X  1.784  =  calcium  carbonate. 

Wt.  calcium  carbonate  X  0.440  =  carbon  dioxide. 

Wt'.  carbon  dioxide  X  8.8068  =  basic  carbonate  of  lead. 

Wt.  of  hydrated  sulphate  of  lime  X  0.4561  =  combined 
sulphuric  acid. 

Wt.  of  combined  sulphuric  acid  X  3.788  =  sulphate  of 
lead. 


CHAPTER  XVII. 

ANALYSIS  OF  WHITE  PAINTS  (continued). 
Analysis  of  White  Paints  According  to  Thompson.1 

331.  Schemes  for  the  separation  of  the  constituents 
from  each  other  and  into  their  proximate  combinations 
depend  on  the  constituents  present,  and  we  can  treat 
this  subject  in  no  better  way  than  by  taking  typical 
cases,  which  we  now  do. 

332.  Sample  1  is  a  mixture  of  barytes,  white  lead,  and 
zinc  oxide. 

Two  1-gram  portions  are  weighed  out.  One  is  dis- 
solved in  acetic  acid  and  filtered,  the  insoluble  matter 
ignited  and  weighed  as  barytes,  the  lead  in  the  soluble 
portion  precipitated  with  bichromate  of  potash,  weighed 
in  Gooch  crucible  as  chromate,  and  calculated  to  white 
lead. 

The  other  portion  is  dissolved  in  dilute  nitric  acid, 
sulphuric  acid  added  in  excess,  evaporation  carried  to 
fumes,  water  added,  the  zinc  sulphate  solution  filtered 
from  barytes  and  lead  sulphate  and  precipitated 
directly  as  carbonate,  filtered,  ignited,  and  weighed  as 
oxide. 

.   333.  Sample  2  is  a  mixture  of  barytes  and  so-called 
sublimed  white  lead. 

Weigh  out  three  1-gram  portions.  In  one  determine 
zinc  oxide,  as  in  case  1.  Treat  a  second  portion  with 
boiling  acetic  acid,  filter,  determine  lead  in  filtrate,  and 
calculate  to  lead  oxide.  Treat  third  portion  by  boiling 

1  J.  Soc.  Chem.  Ind.,  June  30,  1896. 
153 


154  PAINT  AND  VARNISH  PRODUCTS. 

with  acid  ammonium  acetate,  filter,  ignite,  and  weigh 
residue  as  barytes;  determine  total  lead  in  nitrate, 
deduct  from  it  the  lead  as  oxide,  and  calculate  the 
remainder  to  sulphate.  Sublimed  lead  contains  no 
hydrate  of  lead,  and  its  relative  whiteness  is  probably 
due  to  the  oxide  of  lead  being  combined  with  the  sul- 
phate as  basic  sulphate.  Its  analysis  should  be  re- 
ported in  terms  of  sulphate  of  lead,  oxide  of  lead,  and 
oxide  of  zinc. 

334.  Sample  3  is  a  mixture  of  barytes,  sublimed  lead, 
and  white  lead. 

Determine  barytes,  zinc  oxide,  lead  soluble  in 
acetic  acid  and  in  ammonium  acetate,  as  in  case  2; 
also,  determine  carbonic  acid,  which  calculate  to  white 
lead,  deduct  lead  in  white  lead  from  the  lead  soluble 
in  acetic  acid,  and  calculate  the  remainder  to  lead 
oxide. 

335.  Sample  4  is  a  mixture  of  barytes,  white  lead,  and 
carbonate  of  lime. 

Determine  barytes  and  lead  soluble  in  acetic  acid 
(white  lead),  as  in  case  1.  In  filtrate  from  lead  chro- 
mate  precipitate  lime  as  oxalate,  weigh  as  sulphate,  and 
calculate  to  carbonate.  Chromic  acid  does  not  inter- 
fere with  the  precipitation  of  lime  as  oxalate  from 
acetic  acid  solution. 

336.  Sample  5  is  a  mixture  of   barytes,  white  lead, 
zinc  oxide,  and  carbonate  of  lime. 

Determine  barytes  and  white  lead  as  in  case  1.  Dis- 
solve another  portion  in  acetic  acid,  filter,  and  pass  sul- 
phureted  hydrogen  through  the  boiling  solution,  filter, 
and  precipitate  lime  in  filtrate  as  oxalate;  dissolve 
mixed  sulphides  of  lead  and  zinc  in  dilute  nitric  acid, 
evaporate  to  fumes  with  sulphuric  acid,  separate,  and 
determine  zinc  oxide,  as  in  case  1. 


ANALYSIS  OF  WHITE  PAINTS.  155 

337.  Sample  6  is  a  mixture  of  barytes,  white  lead, 
sublimed  lead,  and  carbonate  of  lime. 

Determine  barytes,  lead  soluble  in  acetic  acid  and  in 
ammonium  acetate,  as  in  case  2,  lime  and  zinc  oxide,  as 
in  case  5,  and  carbonic  acid.  Calculate  lime  to  car- 
bonate of  lime,  deduct  carbonic  acid  in  it  from  total 
carbonic  acid,  calculate  the  remainder  of  it  to  white 
lead,  deduct  lead  in  white  lead  from  lead  soluble  in 
acetic  acid,  and  calculate  the  remainder  to  oxide  of 
lead. 

338.  Sample  7  contains  as  insoluble  matter,  barytes, 
china  clay,  and  silica. 

After  igniting  and  weighing  the  insoluble  matter, 
carbonate  of  soda  is  added  to  it  and  the  mixture 
fused.  The  fused  mass  is  treated  with  water  and  the 
insoluble  portion  filtered  off  and  washed.  This  insolu- 
ble portion  is  dissolved  in  dilute  hydrochloric  acid, 
and  the  barium  present  precipitated  with  sulphuric 
acid  in  excess.  The  barium  sulphate  is  filtered  out, 
ignited,  weighed,  and  if  this  weight  does  not  differ 
materially  —  say  by  2  per  cent  —  from  the  weight  of 
the  total  insoluble  matter,  the  total  insoluble  matter 
is  reported  as  barytes.  If  the  difference  is  greater 
than  this,  add  the  filtrate  from  the  barium  sulphate 
precipitate  to  the  water-soluble  portion  of  fusion. 
Evaporate  and  determine  the  silica  and  the  alumina 
in  the  regular  way.  Calculate  the  alumina  to  china 
clay  on  the  arbitrary  formula  2  Si02,  A12O3,  2  H2O, 
and  deduct  the  silica  in  it  from  the  silica,  reporting 
the  latter  in  a  free  state.  It  is  to  be  borne  in  mind 
that  china  clay  gives  a  loss  of  about  13  per  cent  on 
ignition,  which  must  be  allowed  for.  China  clay  is 
but  slightly  used  in  white  paints  as  compared  with 
barytes  and  silica. 


156  PAINT  AND  VARNISH  PRODUCTS. 

339.  Sample  9  contains  sulphide  of  zinc. 

Samples  of  this  character  are  usually  mixtures  in 
varying  proportions  of  barium  sulphate,  sulphide  of 
zinc,  and  oxide  of  zinc.  Determine  barytes  as  matter 
insoluble  in  nitric  acid,  the  total  zinc,  as  in  case  1, 
and  the  zinc  soluble 'in  acetic  acid,  which  is  oxide 
of  zinc.  Calculate  the  zinc  insoluble  in  acetic  acid  to 
sulphide. 

340.  Sample  10  contains  sulphite  of  lead. 

This  is  of  rare  occurrence.  Sulphite  of  lead  is  insol- 
uble in  ammonium  acetate,  and  may  be  filtered  out 
and  weighed  as  such.  It  is  apt  on  exposure  to  the  air 
in  the  moist  state  to  become  oxidized  to  sulphate  of 
lead. 

There  are  certain  arbitrary  positions  which  the 
chemist  must  take  in  reporting  analyses  of  white 
paints : 

1st.  White  lead  is  not  uniformly  of  the  composition 
usually  given  as  theoretical  (2  PbCO3),  (PbH2O2),  but 
in  reporting  we  must  accept  this  as  the  basis  of  calcu- 
lating results,  unless  it  is  demonstrated  that  the  com- 
position of  the  white  lead  is  very  abnormal. 

2d.  In  reporting  oxide  of  lead  present  this  should 
not  be  done  except  in  the  presence  of  sulphate  of  lead, 
and  if  white  lead  is  present,  then  only  where  the  oxide 
is  more  than  1  per  cent ;  otherwise  calculate  all  the  lead 
soluble  in  acetic  acid  to  white  lead. 

3d.  China  clay  is  to  be  calculated  to  the  arbitrary 
formula  given. 

In  outlining  the  above  methods  we  have  in  mind 
many  samples  that  we  have  analyzed,  and  the  combi- 
nations we  have  chosen  are  those  we  have  actually 
found  present. 


ANALYSIS  OF  WHITE  PAINTS.  157 


341.  TYPICAL  ANALYSES  OF   MIXED  PAINTS.1 

I.  II.  III.  IV. 

Color Stone.  Lead  Gray.         White. 

Can l.OOqt.  4.06  qt.         1.06qt.       l.OSqt. 

Contents ,90  qt.  4.01  qt.         1.05qt.         .93  qt. 

Net  weight  ....       2  Ibs.  14  oz.  16  Ibs.  3  oz.     4  Ibs.  3  Ibs.  4  oz. 

Vehicle 50.1  34.2  38.2  36.9 

Pigment 49.9  65.8  61.8  63.1 


100.00  100.00     100.00  100.00 

ANALYSIS  OF  VEHICLE. 

Linseed  oil   ....  68.9  90.4              90.6  89.6 

Benzine  drier  .    .    .    16.1                    3.4  10.1 

Turpentine  drier 9.4                4.0              

Water   .                   .   15.0  0.2                2.0  ,    0.3 


White  lead  .    .    . 
Lead  sulphate 
Zinc  oxide    .    .    . 
Calcium  carbonate 
Barytes     .... 
Silica 


100.00  100.00           100.00  100.00 

ANALYSIS  OF  PIGMENT. 

21.73  49.53            16.64  21.56 

0.85  0.44             13.48  1.09 

47.89  49.64            39.80  49.25 

21.98  10.68  1.80 


18.93 


5.41 


Magnesium  silicate,      25 . 87 

Color,  undeter- 
mined, etc.  .    .    .       2.14  0.39  0.47  0.43 


100.00  100.00  100.00         100.00 

1  Analyses  made  by  author. 

342.  No.  I  is  a  fair  type  of  a  large  number  of  mixed 
paints,  short  in  volume,  short  in  weight,  low  in  pigment, 
nearly  one-third  of  the  vehicle  being  benzine  and  water, 
and  ,27  per  cent  of  total  pigment  inert  material. 

No.  II  is  a  strictly  first-class  paint  in  every  respect,  full 
measure,  16  Ibs.  to  the  gallon,  pure  turpentine  drier,  and 
high  white  lead  content. 

No.  Ill  is  full  measure  and  full  weight.  The  percent- 
age of  drier  is  well  within  the  usually  accepted  limits, 
but  the  manufacturer  obtains  a  considerable  relief  by 
the  use  of  nearly  30  per  cent  of  inert  pigments  costing 


158 


PAINT  AND  VARNISH  PRODUCTS. 


only  a  small  fraction  of  the  price  of  white  lead  or  zinc. 
This  paint  also  has  a  very  small  percentage  of  added 
water. 

No.  IV  is  7  per  cent  short  in  volume,  is  low  in  lead  pig- 
ments, and  contains  nearly  28  per  cent  of  inert  pigment, 
which  in  this  case  is  mainly  magnesium  silicate. 

343.  Calculation  of  the  approximate  cost  of  mixed 
paints  using  No.  I  and  No,  II  as  types. 

COST  OF  VEHICLE. 


No 

I. 

No 

.11. 

Liquid. 

Cost  per 
Gallon. 

Gal. 

Total 
Cost. 

Gal. 

Total 
Cost. 

Linseed  oil    ... 
Turpentine  drier  . 

$0.40 
1.00 

68.9 

$27.56 

90.4 
9.4 

$36.16 
9  40 

Benzine  drier   .    . 

0.0326 

16.1 

5.25 

Water     

0.00 

15  0 

0.00 

0.2 

100      gallons  (750  pounds),  No.  I,  cost  $32.81. 
1      pound  costs  $0.0438. 

50 . 1  pounds  cost  $2 . 19. 

100      gallons  (750  pounds),  No.  II,  cost $45. 56. 
1     pound  costs  $0.0607. 

34. 2  pounds  cost  $2.09. 

COST  OF  PIGMENT. 


No 

I. 

No. 

II. 

Pigment. 

Cost  per 
Lb 

Lbs. 

Total 
Cost. 

Lbs. 

Total 
Cost. 

White  lead    .    .    . 
Lead  sulphate  l    . 
Zinc  oxide     .    .    . 
Inert  pigments 

$0.065 
0.05 
0.05 
0  01 

21.73 
0.85 
47.89 
27  39 

$1.41 
0.04 
2.39 
0  27 

49.53 
0.44 
49.64 

$3.22 
0.02 
2.48 

Color  ! 

0  05 

2  14 

0.11 

0.47 

0.02 

Lead  sulphate  present  in  *he  zinc  oxide. 


ANALYSIS  OF  WHITE  PAINTS.  159 

100      pounds  total  pigment,  No.  I,  cost  $4.22. 

1      pound  costs  $0.042. 
49.9  pounds  cost  $2.11. 

100      pounds  total  pigment,  No.  II,  cost  $5 . 74. 
1      pound  costs  $0 . 057. 

65 . 8  pounds  cost  $3.75. 

No.  I. 

50 . 1  pounds  liquid  cost $2 . 19 

49 . 9  pounds  pigment  cost 2.11 


100 . 0  pounds  paint  cost      $4 . 30 

1 . 0  pound  paint  costs      0 . 043 

1      gallon  (2  pounds  14  ounces)  X  4  costs  .    .  0.495 

No.  II. 

34 . 2  pounds  liquid  cost $2 . 09 

65.8  pounds  pigment  cost 3.75 


100  .  0  pounds  paint  cost      ..........     $5  .  84 

1      pound  paint  costs      .    .........       0  .  0584 

1      gallon  (or  16  pounds  3  ounces)  costs     .    .       0  .  945 

In  other  words,  one  paint  costs  almost  exactly  twice 
as  much  as  the  other,  as  regards  paint  and  oil  ingredi- 
ents. The  cost  of  the  can  (gallon  size),  label,  and  crate 
is  about  10  cents.  Salesmen's  commissions,  salary, 
and  traveling  expenses  are  about  5  cents  per  gallon; 
the  cost  of  manufacture,  depreciation  of  plant  and 
machinery,  6  to  8  cents  per  gallon. 

It  must  also  be  borne  in  mind  that  the  cost  of  crude 
materials  has  advanced  markedly  during  the  last  few 
years.  The  following  table  prepared  by  the  Paint 
Manufacturers'  Association  shows  the  increase  in  cost 
of  "various  paint  materials  in  1907  as  compared  with 
1897: 


White  lead   .................  61.8 

Zinc  oxide    .................  40  .  5 

Barium  sulphate  ...............  44.2 

Linseed  oil   ................    .  45  .  4 

Turpentine  .................  155.0 

Japan  drier  .......    ...........  42.0 

Tin  cans   ......    .    ...........  33.0 

Packing  boxes     .    ,    50*    ...........  64  .  2 


160 


PAINT  AND  VARNISH  PRODUCTS. 


344.  ANALYSES  OF  SUBLIMED  LEAD  PAINTS  BY  AUTHOR. 


I. 

II. 

III. 

IV. 

White. 

White. 

Pearl  Gray. 

White. 

Net  weight,  Ibs.  and 

oz.  .    .       15 

15:1 

14:8 

3:20 

Capacity  of  can,  qts. 

.    .    .         3.96 

4.00 

4.00 

1.03 

Contents,  qts. 

.    .    .         3.95 

3.94 

3.86 

.95 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Pigment  by  weight  . 

.     .     .         57.0 

59.2 

58.6 

64.8 

Vehicle  by  weight     . 

.    .    .       43.0 

40.8 

41.4 

35.2 

100.0 

100.0 

100.0 

100.0 

ANALYSIS  OF  VEHICLE. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

...       90.5 

90  4 

90.4 

84.5 

Drier  

.    .    .         9.31 

9.5 

9.6 

6.4 

Water     

...         0.2 

0.1 

0.0 

9.1 

100.0 

100.0 

100.0 

100.0 

ANALYSIS  OF 

PIGMENT. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

White  lead  

...           0.00 

0  00 

0  00 

0  00 

Lead  sulphate  2     .    . 

.    .    .       58.37 

33.46 

35.56 

59  09 

.    .    .         5.99 

9.63 

8  93 

16  01 

Zinc  oxide      .... 

.    .    .       35.24 

56.38 

55  11 

5  18 

Barium  sulphate  .    . 

.    .    .         0.00 

0  00 

0  00 

19  08 

Undetermined  color, 

etc.     .         0.40 

0.53 

0.40 

0.64 

1  Benzine. 


100.00        10000         100.00 
2  Sublimed  lead. 


100.00 


In  the  above  analyses  the  percentage  of  zinc  oxide 
incidental  to  the  manufacture  of  sublimed  lead  is  in- 
cluded in  the  total  zinc  oxide. 

345.  ANALYSES  OF  LEADED  ZINC   PAINTS   BY   AUTHOR. 


I. 

II. 

III. 

IV. 

Lead 
Color. 

White. 

Blue. 

Gray. 

Net  weight,  Ibs.  and  oz.  .    . 

6:14 

3:8 

0  :14.5 

5:10 

Capacity  of  can,  qts.    .    .    . 

1.91 

1.06 

.33 

1.95 

Contents,  qts    

1.82 

1.00 

.28 

1.70 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Pigment  by  weight  .... 
Vehicle  by  weight     .... 

58.9 

41.1 

60.7 
39.3 

57.0 
43.0 

57.8 
42.2 

100.0 


100.0 


100.0 


100.0 


ANALYSIS  OF  WHITE  PAINTS. 


161 


ANALYSIS  OF  VEHICLE. 


Linseed  oil  . 
Benzine  drier 
Water 


80.2 

8.5 

11.3 

100.0 


56.9 
20.6 
22.5 

100.0 


60.4 
25.7 
13.9 

100.0 


77.6 

7.9 

14.5 

100.0 


ANALYSIS  OF  PIGMENT. 

Per  cent.  Per  cent. 

White  lead 

Lead  sulphate 39.26  18.13 

Zinc  oxide 34.20          34.04 

Calcium  carbonate   ....         5.39  41.09 

Barytes 19.90  6.20 

Undetermined  color,  etc.     .         1 . 25  0 . 54 


Per  cent.       Per  cent. 


17.77 

33.58 

39.88 

6.40 

2.371 


14.23 

37.57 

41.70 

6.10 

0.40 


100.00         100.00         100.00         100.00 
346.  ANALYSES  BY  AUTHOR  OF  MIXED  PAINTS  FOR 


INSIDE   USE. 


I. 

Inside 

White. 


II. 


III. 

Inside 
White. 


White. 

Net  weight,  Ibs.  and  oz 3:0  15  :  0  14  :  2 

Capacity  of  can,  qts 1.04  0.30  0.30 

Contents,  qts 0.99  0.26  0.24 

Per  cent.  Per  cent.  Per  cent. 

Pigment 62.9  28.3  62.8 

Vehicle 37.1  71.7  37.2 

100.0  100.0  100.0 
VEHICLE. 

Per  cent.  Per  cent.  Per  cent. 

Linseed  oil 60. 12  68. 6 2  77.9 

Turpentine 39.9  30.0  22.1 

Water 0.0  1.4  0.0 

100.0  100.0  100.0 
PIGMENT. 

*"  .  Per  cent.  Per  cent.  Per  cent. 

White  lead 18.84 

Lead  sulphate 2 . 57  

Zinc  oxide 70 . 27  99 . 80  80 . 45 

Lithopone 26 . 33  

Barium  sulphate 20 . 12       

Zinc  sulphide 6. 13  

Silica 0 . 28  

Undetermined  .  0.55  0.20  00.71 


100.00         100.00 

1  Color  largely  organic. 

2  Includes  a  small  amount  of  dammar  varnish. 


100.00 


162 


PAINT  AND  VARNISH  PRODUCTS. 


347.  ANALYSES  OF  CHEAPENED  MIXED  PAINTS 
BY.THE  AUTHOR. 

Showing  the  various  devices  used  for  cheapening 
the  cost  of  production,  —  short  volume,  low  pigment 
content,  practical  absence  of  all  lead  pigments,  excessive 
use  of  drier,  high  per  cent  of  water  and  of  cheap  inert 
pigments.  Two  of  these  brands  were  sold  as  straight 
white  lead  and  zinc  oxide  paints. 


I. 

II. 

White. 

Gray. 

Net  weight,  Ibs.  and  oz. 

3:0 

6:3 

Capacity  of  can,  qts.    . 

1.03 

1.95 

Contents  qts 

99 

1.92 

Per  cent. 

Per  cent. 

Pigment  by  weight  .    . 
Vehicle 

.    .        55.1 
44  9 

54.6 
45.4 

100.0 

100.0 

ANALYSIS  OF  VEHICLE. 

Per  cent. 

Per  cent. 

Linseed  oil             .    .    . 

72  5 

54.  4  l 

Benzine  drier     .... 

9   1 

28.9 

Water     

18  4 

16.7 

100.0 

100.0 

ANALYSIS  OF 

PIGMENT. 

Per  cent. 

Per  cent. 

White  lead     

Lead  sulphate    .... 

89 

3   11 

Zinc  oxide  

.    .       53.86 

24.67 

Calcium  carbonate   .    . 

.    .       43.39 

40.07 

Magnesium  carbonate 

0.73 

Barytes 

22.10 

Silica 

0  60 

7.26 

Undetermined  color,  etc 

.53 

2.79 

III. 

Lead 
Color. 

9:9 

3.37 

2.42 

Per  cent. 
67.10 
32.90 

100.0 


Per  cent. 

83. 91 

4.3 

11.8 

100.0 


100.00 


4.73 
24.34 
4.47 

66  .'26 
6.20 
100.00         100.00 


IV. 

Slate 
Color. 

5:12 
1.90 
1.85 

Per  cent. 
50.8 
49.2 

100.0 


Per  cent. 
61.9 
22.0 
16.1 

100.0 


Per  cent.        Per  cent. 


0.74 
60.10 
21.11 


16.25 
1.80 

100.00 


Very  low-grade  linseed  oil. 


CHAPTER  XVIII. 

KALSOMINE,  COLD-WATER  PAINTS,  AND  FLAT  WALL 
FINISHES. 

348.  Kalsomine.     Kalsomines  may  be  divided  into 
two  classes,  —  those  which  require  hot  water  to  de- 
velop their  adhesive  strength  and  those  which  may 
be  mixed  with  cold  water,  the  glue  having  been  so 
treated  as  to  be  soluble  in  cold  water.     Kalsomines  of 
the  latter  class  are  more  convenient  to  use  but  more 
difficult  to  manufacture.     Either  class,  however,  con- 
sists essentially  of  glue  and  one  or  more  of  the  following 
inerts,  whiting,  china  clay,  gypsum,  magnesium  silicate, 
together  with  the  necessary  tinting  colors. 

349.  The   essential   qualities    of  a  good  kalsomine 
are: 

1.  Ease  of  preparation  with  water,  with  quick  de- 
velopment of  adhesive  strength. 

2.  Opacity  and  freedom  from  chalking. 

3.  Absence  of  brush  marks  and  lap  streaks  on  appli- 
cation. 

4.  Maintenance  of  "  sweetness "  for  at  least  3  days 
after  having  been  mixed  with  water. 

.-  5.  Permanence  of  tints. 

350.  Whiting  is  undoubtedly  the  best  white  base  for 
kalsomine,  as  it  possesses  the  greatest  body,  the  other 
three  inerts  being  more  transparent,  but  spread  easier 
under  the  brush,  so  that  the  majority  of  kalsomines 
contain  besides  the  whiting  a  percentage  varying  from 
20  to  40  of  these  other  inerts.     Chalking  is  caused  by 
using  an  insufficient  amount  of  glue  or  having  weakened 

163 


164  PAINT  AND  VARNISH  PRODUCTS. 

the  strength  of  the  glue  by  the  excessive  use  of  pre- 
servatives, a  certain  amount  of  which  must  be  used  in 
order  to  maintain  the  "  sweetness "  for  several  days 
after  a  batch  has  been  mixed  with  water,  as  the  price 
at  which  kalsomine  is  sold  precludes  the  use  of  high- 
priced  glues.  The  best  and  most  generally  used  pre- 
servatives are  aluminum  sulphate  and  zinc  sulphate, 
and,  as  above  stated,  their  excessive  use  weakens  the 
glue.  When  mixed  with  water,  a  kalsomine  should 
"jell"  properly,  and  when  applied  on  a  wall  the  edges 
of  the  first  section  should  not  dry  before  the  next  sec- 
tion is  started,  else  the  lap  will  show.  The  retarding 
of  the  drying  of  a  kalsomine  can  be  accomplished  by 
the  use  of  Irish  moss. 

351.  Permanence  of  tints  is  secured  by  avoiding  colors 
which  are  affected  by  the  alkali  action  of  the  lime  in 
the  plaster,  especially  Prussian  or  Chinese  blue  and 
chrome  green,  using  in  their  place,  as  much  as  possible, 
blue  and  green  lakes,  which  are  known  as  "lime  proof." 
The  various  yellows  are  obtained  by  the  acid  of  ocher 
and  the  chrome  yellows;  the  reds  with  the  iron  oxide 
pigments,  para  reds  precipitated  on  an  inert  base  and 
to  some  extent  other  organic  reds ;  the  greens  with  lime- 
proof  green  lakes  and  chrome  greens,  although  the  lat- 
ter are  not  permanent;  the  blues  are  lime-proof  blue 
lakes  and  ultramarine  blue.     The  intermediate  colors 
are  obtained  by  intermixing  the  above  and  with  the 
aid  of  the  siennas,  umbers,  and  blacks. 

352.  Analysis.     The  analysis  of  kalsomines  offers  no 
particular  difficulties,  the  percentage  of  glue  being  ob- 
tained by  running  a  nitrogen  determination  by  the 
Kjeldahl  method  and  multiplying  by  the  factor  0.37. 
Zinc  sulphate  and  aluminum  sulphate  are  detected  and 
estimated  in  the  usual  manner;  the  white  base  and 


KALSOMINE,  COLD-WATER  PAINTS,  ETC.          165 

tinting  colors  by  the  usual  analytical  methods,  the 
percentage  of  lake  colors  being  obtained  by  difference. 
353.  The  following  analyses  made  by  the  author  are 
representative  of  several  of  the  leading  combinations  on 

the  market : 

i.  ii. 

White.  White. 

Per  cent.          Per  cent. 

Whiting 63.7  68.2 

China  clay 16.3  9.1 

Gypsum 10.1  15.5 

Glue 5.5  4.0 

Aluminum  sulphate 1.4  2.1 

Moisture 2.5  0.4 

Ultramarine  blue trace           

Undetermined 0.5  0.7 


100.0          100.0 

Yellow  Tint. 
Per  cent. 

Whiting    . 60.1 

China  clay 15.0 

Gypsum 11.3 

Ocher 2.4 

Lead  chromate 2.4 

Moisture 1.9 

Glue 5.1 

Alum  sulphate 0.9 


100.0 

Solid  Wall  Red. 
Per  cent. 

Clay 22.2 

Red  lake 9.4 

Barium  sulphate 63 . 1 

Glue 4.9 

Moisture 0.4 

100.0 


354.  Lakes.  The  lime-proof  lakes  used  are  usually  on 
a  barium  carbonate  or  sulphate  base,  less  commonly  on 
a  silica  or  silicate  base,  and  this  base  in  the  case  of  solid 
wall  colors,  so-called,  will  constitute  the  larger  portion 
of  the  kalsomine. 


166  PAINT  AND  VARNISH  PRODUCTS. 

355.  Testing.  Hot -water  kalsomines  are  prepared  by 
simply  grinding  together  the  glue,  white  base,  and  tint- 
ing colors,  after  mixing  in  a  high-speed  rotary  mill.  In 
the  manufacture  of  the  cold-water  kalsomines  the  glue 
is  given  a  special  treatment  to  render  it  soluble  in  cold 
water  before  it  is  incorporated  with  the  pigments,  the 
mixing  and  grinding  being  accomplished  in  the  usual 
manner.  The  testing  of  the  glue  for  strength  and 
sweetness  is  a  most  important  consideration,  especially 
in  the  manufacture  of  cold-water  kalsomines.  The 
method  adopted  by  the  author  is  to  prepare  a  small 
batch  of  kalsomine  according  to  the  regular  formula, 
incorporating  the  ingredients  in  the  mixer  and  grind- 
ing in  the  mill  in  the  usual  manner,  the  glue,  how- 
ever, being  the  one  item  omitted  completely,  and  the 
base  so  obtained  is  kept  in  the  laboratory  for  testing 
purposes.  The  weighed  sample  of  the  glue  which 
has  been  melted  in  the  calculated  amount  of  hot  water 
is  cooled  to  room  temperature  and  the  requisite  amount 
of  kalsomine  base  added,  care  being  taken  to  obtain  a 
mix  free  from  lumps.  A  portion  is  brushed  out  uni- 
formly on  a  sheet  of  unglazed  paper,  allowed  to  dry, 
and  the  adhesiveness  noted  by  rubbing  and  by  the 
folding  of  the  paper.  The  remainder  is  allowed  to 
stand  loosely  covered  in  the  laboratory  for  3  days,  it 
then  being  stirred  up  and  the  " sweetness"  noted.  It 
is  a  peculiar  fact  that  a  glue  which  when  melted  up  in 
water  and  allowed  to  jell  will  keep  sweet  by  itself  for 
3  days  may  undergo  marked  decomposition  in  36  hours 
when  incorporated  with  the  pigment  portion  of  the 
kalsomine.  Usually  the  deep  tints  and  solid  wall  colors 
will  not  require  the  addition  of  a  glue  preservative,  as 
the  tinting  colors  themselves  will  prevent  the  decom- 
position of  the  glue. 


KALSOM1NE,   COLD-WATER  PAINTS,   ETC.          167 

356.  Cold-water  paints.    The  paints  which  come  under 
this  head  are  prepared  very  much  like  kalsomine  except 
that  the  binding  agent  instead  of  glue  is  casein,  together 
with  sodium  carbonate  or  quicklime  or  both,  which  are 
added  in  the  dry  form,  the  combination  with  the  casein 
being  affected  on  the  addition  of  water  when  being  pre- 
pared for  use.     The  tints  are  usually  restricted  to  those 
obtained  with  ochre,  blacks,  and  cheap  Venetian  reds. 
Unless  kept  in  a  tight  package  cold-water  paints  will 
lose  their  strength,  as  the  quicklime  will  absorb  carbon 
dioxide  from  the  air,  becoming  inert.     Caustic  soda  is 
sometimes  used,  but  possesses  marked  disadvantages. 

357.  Analyses.    The  following  analyses  by  the  author 
afford  some  idea  of  the  composition  of  this  class  of 

paints: 

i.  n. 

Outside  White.  Inside  White. 

Per  cent.  Per  cent. 

Whiting 55.55  60.60 

Clay 13.90  14.12 

Calcium  sulphate 13.65  16.08 

Casein 9.03  6.05 

Calcium  oxide 4.72  1.51 

Sodium  hydroxide 

Sodium  carbonate 3.15  1.64 

Ultramarine  blue  .  trace 


100.00         100.00 

358.  Specifications  for  Cold- Water  Paint,  Navy  Depart- 
ment, 1908. 

1.  Cold-water  paint  shall  consist  of  whiting,  20  to 
25  per  cent  silicious  matter,  free  lime  equivalent  to 
from  5  to  10  per  cent  of  calcium  hydrate,  Ca(OH)2,  and 
from  10  to  12  per  cent  of  casein,  with  not  more  than 
traces  of  calcium  sulphate  and  small  amounts  of  zinc 
oxide. 

2.  It  must  be  capable  of  readily  remixing  at  the  end 
of  fifteen  hours  after  having  been  mixed  in  proper  pro- 


168  PAINT  AND  VARNISH  PRODUCTS. 

portions  with  cold  water,  and  must  not  possess  an 
offensive  odor. 

3.  When  dry  the  paint  must  be  of  white  color,  and 
not  chip,  scale,  powder,  or  rub  off  when  washed  with 
cold  water,  and  in  these  regards  must  be  equal  to 
standard  sample. 

359.  Flat   wall  finishes.     During  the  last  few  years 
there  has  been  developed  a  demand  for  a  flat  wall  finish 
similar  to  that  produced  by  kalsomine,  but  capable 
of   being  washed   and  cleaned   and  not  affected   by 
moisture. 

360.  The  pigments  used  for  this  purpose  must  have 
a  high   degree   of    opacity,    lithopone   perhaps   being 
the  one  most  used  for  the  white  and  as  a  base  for 
the   tints,    although    Paris   white    and    gypsum   may 
replace    the    lithopone    in    some   of   the   tints,   espe- 
cially the  yellows  and  greens.     The  most  permanent 
blues  are  obtained  with  ultramarine;  lime-proof  reds 
are  used  where  possible;  and  the  yellow  tints  are  pro- 
duced with  chrome  yellow  and  to  some  extent  with 
ocher. 

361.  The  ratio  of  vehicle  to  pigment  is  much  the 
same  as  in  ordinary  mixed  paints.     The  desired  flat 
effect  is  obtained  by  the  use  of  a  large  percentage 
of  volatile  thinners,  which  will  constitute  about  75 
per  cent  of  the  vehicle.     The  volatile  thinners  used 
may  be  a  mixture  of  turpentine  and  benzine,  or  tur- 
pentine  and  petroleum  spirits,   or  petroleum  spirits 
only. 

362.  The  remaining  portion  of  the  vehicle,  which  is 
just  sufficient  in  quantity  to  act  as  a  binder  for  the 
pigment,  may  be  a  special  varnish  or  a  mixture  of 
boiled  oil  and  a  varnish,  such  as  a  linseed  oil-rosin 
varnish. 


KALSOMINE,  COLD-WATER  PAINTS,  ETC.         169 

363.  Analyses.    The  following  analyses  are  typical  of 
this  class  of  finishes : 

White.  Yellow. 

Per  cent.  Per  cent. 

Lithopone 68.4  12.1 

Gypsum      24.0 

Chrome  yellow 23 . 9 

Petroleum  thinner 23 . 5  29 . 7 

Linseed  oil  and  varnish 8.1  10.3 

100.0  100.0 


CHAPTER  XIX. 

COMPOSITION  OF  COLORED  PAINTS. 

364.  Lack  of  uniformity.     After  the  extraction  of  the 
vehicle  it  is  necessary  to  examine  the  pigment  quali- 
tatively in  order  to  ascertain  the  ingredients  to  be 
determined.     The  usual  qualitative  scheme  may  be 
followed  with  advantage.     The  colors,  as  given  on  the 
color  cards  of  paint  manufacturers,  are  usually  confined 
to  a  limited  number  of  combinations,  the  possible  com- 
ponents of  which  may  be  easily  ascertained,  and  which, 
in  fact,  are  usually  well  known  to  paint  chemists;  but 
to  the  chemist  who  has  had  but  little  experience  along 
paint  lines,  the  following  tables  of  color  ingredients  will 
be  of  interest.     Unfortunately,  manufacturers  are  not 
agreed  among  themselves  as  to  standards  for  naming 
colors;  for  example,  a  tea  green  put  up  by  one  manu- 
facturer may  not  correspond  with  a  tea  green  put  up 
by  another;  but,  by  a  careful  study  of  the  color  cards 
issued  by  reputable  paint  manufacturers,  it  is  usually 
possible  to  identify  the  color  to  be  analyzed.     Also  the 
same  or  nearly  the  same  color  may  be  produced  by 
different  combinations  of  color  pigments,  hence  it  is 
necessary  to  state  all  of  the  possible  constituents  that 
may  be  used,  as  far  as  the  author  has  been  able  to 
ascertain  them,  even  though  it  is  quite  probable  that 
they  may  not  all  be  present  in  the  same  paint. 

365.  Reds: 

Brick.    Base  white,  ochre  and  Venetian  red. 
Flesh  Color.    Base  white,  ochre,  Venetian  red,  and 
sometimes  orange  chrome  yellow. 

170 


COMPOSITION  OF  COLORED  PAINTS.  171 

Indian  Red.     Indian  red. 

Lilac.  Ultramarine,  carmine,  Indian  red,  ochre,  lamp- 
black. 

Maroon.  Carmine,  ultramarine,  lampblack,  Tuscan 
red. 

Pink;     Base  white,  orange  chrome  yellow. 

Terra  Cotta.  Base  white,  burnt  sienna,  umber, 
chrome  yellow,  Venetian  red,  ochre. 

Salmon.  Base  white,  vermilion,  lemon  chrome  yel- 
low, sienna,  ochre,  Venetian  red,  orange  mineral. 

Tuscan  Red.   Tuscan  red,  Indian  red,  Para  vermilions. 

Venetian  Pink.     Base  white,  Venetian  red. 

Venetian  Red.     Venetian  red. 

366.  Blues: 

Azure  Blue.     Base  white,  ultramarine  blue,  chrome 

green,  Prussian  blue. 
Bronze  Blue.     Black,  Prussian  blue. 
Dark  Blue.     Base   white,    chrome   green,   Prussian 

blue,  ultramarine,  black. 

Light  Blue.     Base  white,  ultramarine,  Prussian  blue. 
Neutral  Blue.     Base  white,  Prussian  blue,  umber, 

black. 
Robin's  Egg  Blue.     Base  white,  ultramarine,  lemon 

chrome  green. 
Sky  Blue.     Base  white,  cobalt  blue,  Prussian  blue, 

ultramarine  blue,  chrome  yellow. 

367.  Yellows: 

Buff.     Base  white,  ochre,  black,  red  chrome  lead. 
Canary.     Base  white,  lemon  chrome  yellow,  chrome 

green. 
Citron.     Base  white,  Venetian  red,  Prussian  blue, 

chrome  yellow. 


172  PAINT  AND  VARNISH  PRODUCTS. 

Cream.    Base  white,  ochre,  Venetian  red. 

Deep  Cream.    White,  ochre,  Venetian  red. 

Ecru.    Base   white,   ochre,   chrome   yellow,   black, 

chrome  green. 

Ivory.     Base  white,  chrome  yellow,  ochre. 
Lemon.     Base  white,  chrome  yellow. 
Manilla.     Base  white,  ochre,  chrome  yellow. 
Stone.     Base  white,  ochre,  umber,  chrome  yellow. 
Straw.     Base  white,  chrome  yellow,  ochre,  Venetian 

red. 

368.  Greens: 

Ivy  Green.     Ochre,  lampblack,  Prussian  blue. 

Light  Green.     White,  Prussian  blue,  chrome  green. 

Manse  Green.     Chrome  green,  chrome  yellow,  ochre. 

Moss  Green.  Base  white,  ochre,  chrome  green,  lamp- 
black. 

Olive  Green.  Lemon  chrome  yellow,  ochre,  ultrama- 
rine blue,  Prussian  blue,  Indian  red,  chrome  green, 
lampblack. 

Pea  Green.  Base  white,  chrome  green,  very  rarely 
emerald  green. 

Sap  Green.  Base  white,  chrome  yellow,  lampblack, 
chrome  green. 

Sea  Green.     Base  white,  chrome  green,  sienna,  ochre. 

Tea  Green.  Base  white,  chrome  green,  chrome  yel- 
low, lampblack. 

Willow  Green.  Base  white,  chrome  green,  umber, 
ivory,  black. 

369.  Browns: 

Acorn  Brown.     Sienna,  carmine,  Indian  red,  lamp- 
black, ochre. 
Brown.     Indian  red,  lampblack,  ochre. 


COMPOSITION  OF  COLORED  PAINTS.  173 

Chocolate.     Similar  to  acorn  brown. 

Cork  Color.  Base  white,  ochre,  Indian  red,  lamp- 
black, umber. 

Dark  Drab.  Base  white,  Indian  red,  lampblack, 
Prussian  blue,  yellow  ochre. 

Doe  Color.  Base  white,  sienna,  umber,  ochre,  lamp- 
black. 

Dove  Color.  Base  white,  Prussian  blue,  lampblack, 
ochre,  Indian  red,  umber,  sienna. 

Drab.  Base  white,  umber,  Venetian  red,  yellow  ochre, 
black. 

Fawn.  Base  white,  ochre,  Indian  red,  lampblack, 
sienna,  umber,  chrome  yellow,  Venetian  red. 

Lava.  Base  white,  black,  chrome  orange,  chrome 
yellow. 

Sandstone.     Umber. 

Snuff  Brown.  Base  white,  ochre,  Indian  red,  Vene- 
tian red. 

370.  Greys  and  grays:1 

Ash  Gray.  Base  white,  ochre,  lampblack,  sienna, 
ultramarine  blue. 

Dark  Slate.     Base  white,  Prussian  blue,  lampblack. 

French  Gray.  Base  white,  black,  ultramarine  Prus- 
sian blue,  Venetian  red. 

Granite.     Base  white,  ochre,  lampblack. 

Graystone.  Base  white,  black,  Prussian  blue,  ultra- 
marine, Venetian  red. 

Lead.     Base  white,  lampblack,  Prussian  blue. 

Light  Grey.     Base  white,  lampblack,  Prussian  blue. 

1  Grey  is  understood  to  mean  an  admixture  of  black  and  white, 
while  gray  is  an  admixture  of  black  and  white  to  which  another  color 
has  been  added,  provided,  of  course,  that  the  black  and  white  pre- 
dominate. 


174  PAINT  AND  VARNISH  PRODUCTS. 

Pearl.     Similar  to  French  gray. 

Silver  Gray.     Base  white,  ochre,  lampblack,  chrome 

yellow. 

Smoke  Gray.    Base  white,  ochre,  lampblack. 
Steel  Gray.     Base  white,  chrome  yellow,  lampblack. 
Stone  Gray.     Base  white,  chrome  yellow,  black. 
Warm  Gray.     Base  white,  ochre,  lampblack,  sienna, 

Prussian  blue. 


CHAPTER  XX. 

ANALYSIS    OF   INDIAN  REDS,  VENETIAN  REDS,  TUSCAN 
REDS,  RED  OXIDES,  AND  OCHRES. 

371.  Hygroscopic  moisture.     Heat  2  grams  at  105°  C. 
for  3  hours.     Loss  in  weight  represents  hygroscopic 
moisture. 

372.  Combined   water,   etc.     Transfer  above  sample 
to  a  weighed  platinum  crucible  and  heat  for  one  hour 
over  an  ordinary  lamp,  or  better  in  a  muffle.     Loss  in 
weight  indicates  amount  of  combined  water.     Carbon- 
ates and  organic  matter  render  the  results  inaccurate, 
in  which  case  continue  the  ignition  at  bright  red  heat 
for  several  hours,   and  weigh  again.     Determine  the 
carbon  dioxide  in  another  portion  of  the  sample  and 
estimate  the  combined  water  by  difference.     If  a  large 
amount  of  calcium  sulphate  is  present,  it  is  possible  to 
heat  it  strongly  enough  to  partially  drive  off  the  com- 
bined sulphuric  acid,  and  unless  this  be  taken  account 
of  the  analysis  will  total  up  to  more  than  100  per  cent. 
In  the  case  of  a  Tuscan  red  which  has  precipitated  upon 
it  an  organic  color,  the  loss  in  weight  is  best  reported 
as  combined  water  and  organic  matter.     The  presence 
of  .an  organic  color  may  always  be  detected  by  the 
characteristic  odor  given  off  at  the  beginning  of  the 
ignition. 

373.  Silica  and  barium  sulphate.     One  gram  of  the 
pigment  is  intimately  mixed  with  6  to  8  grams  of  potas- 
sium bisulphate  and  fused  in  a  large  porcelain  crucible, 
the  cover  of  which  is  small  enough  to  set  inside  the  top 
of  the  crucible,  at  not  too  high  a  temperature  for  one- 

175 


176  PAINT  AND  VARNISH  PRODUCTS. 

half  hour,  finally  heating  the  side  of  the  crucible  to 
finish  the  conversion  of  any  material  adhering  to  the 
cover  and  upper  portion  of  the  crucible.  The  iron, 
aluminum,  calcium,  and  magnesium  are  converted  into 
sulphates,  the  barytes  remains  unchanged  and  the  silica 
is  completely  dehydrated.  With  a  little  care,  using  a 
low  heat  at  first,  the  fusion  may  be  conducted  with  very 
little  frothing  or  spattering.  Fusion  with  bisulphate  is 
to  be  preferred  to  solution  with  hydrochloric  acid,  as 
ferric  chloride  is  appreciably  volatile  on  boiling.  Also 
the  silicates  of  iron  that  are  present  in  small  quantity 
in  the  natural  oxides  are  not  decomposable  with  hydro- 
chloric acid. 

After  cooling,  the  entire  contents  of  the  crucible  may 
be  shaken  loose  and  dissolved  in  sufficient  water  and  a 
little  hydrochloric  acid.  Filter  and  make  up  to  250  c.c. 
unless  calcium  is  present  in  large  amount,  in  which  case 
make  up  to  a  volume  of  not  less  than  500  c.c.,  as  calcium 
sulphate  is  but  sparingly  soluble. 

The  residue  remaining  on  the  filter  is  ignited  and 
weighed  in  a  platinum  crucible.  The  residue  is  tested 
for  barium  sulphate  by  the  flame  test:  if  absent  the 
residue  is  reported  as  silica;  if  present  the  residue  is 
treated  in  the  crucible  with  hydrofluoric  acid  until  a 
thin  paste  is  formed.  The  mixture  is  stirred  with  a 
platinum  wire  and  digested  at  a  gentle  heat;  finally  two 
or  three  drops  of  sulphuric  acid  are  added,  and  the 
temperature  gradually  raised  until  no  further  loss  in 
weight  takes  place,  indicating  that  the  silica  has  been 
completely  expelled.  The  residue  is  weighed  as  barium 
sulphate,  and  the  loss  in  weight  represents  the  silica, 
or  the  residue  of  barium  sulphate  and  silica  may  be 
fused  with  sodium  carbonate  as  described  under  the 
analysis  of  white  pigments. 


ANALYSIS  OF  INDIAN  REDS,   ETC.  177 

374.  Ferric  oxide.    An  aliquot  portion  of  the  solution 
from  373  is  heated  to  boiling  and  stannous  chloride 
solution  added  cautiously  until  the  yellow  color  has 
disappeared,  and  then  a  slight  excess  added.     All  at 
once,  with  vigorous  shaking  of  the  flask,  50  c.c.  of  mer- 
curic chloride  solution  is  added,  then  50  c.c.  of  the 
manganous  sulphate  solution.     Dilute  with  cold  fresh- 
boiled  water  and  titrate  with  permanganate  solution. 
Calculate  iron  found  to  ferric  oxide. 

375.  Preparation  of  reagents. 

a.  Stannous  chloride.     Dissolve  30  grams  of  tin  in 
250  c.c.  of  hydrochloric  acid,  filter  through  glass  wool, 
and  make  up  to  one  litre. 

b.  Mercuric  chloride.     Dissolve  50  grams  in  one  litre. 

c.  Manganous  sulphate.    One  litre  should  contain  66.7 
grams  of  crystallized  manganous  sulphate,   333   c.c. 
phosphoric  acid  (sp.  gr.  1.3),  and  133  c.c.  of  cone,  sul- 
phuric acid. 

d.  Potassium  permanganate.     Dissolve  3.16  grams  in 
one  litre;  standardize  against  the  standard  iron  solution. 

e.  Standard  iron  solution.     Dissolve  7.03  grams  iron 
wire,  99.7  per  cent  purity,  in  dilute  hydrochloric  acid; 
make  to  one  litre. 

1  c.c.  =  0.01  g.  ferric  oxide  or  0.007  gr.  iron. 
In  many  cases  where  a  rapid  commercial  determina- 
tion of  the  iron  content  alone  is  desired,  the  pigment 
may  be  dissolved  in  hydrochloric  acid,  with  the  subse- 
quent addition  of  a  few  drops  of  nitric  acid,  filtered, 
the  iron  and  alumina  precipitated  with  ammonia;  after 
thorough  washing  dissolved  in  sulphuric  acid,  run 
through  a  "redactor,"  such  as  may  be  obtained  from 
any  of  the  leading  supply  houses,  and  then  simply 
titrated  with  standard  permanganate  solution  in  the 
usual  manner. 


178  PAINT  AND  VARNISH  PRODUCTS. 

376.  Alumina.     An  aliquot  part  of  the  solution  in  373 
is  made  just  alkaline  with  ammonia,  boiled,  decanted, 
filtered,   washed,   redissolved,   reprecipitated,   filtered, 
ignited,  and  weighed  as  alumina  and  ferric  oxide,  the 
alumina  being  obtained  by  difference. 

377.  Calcium.     The  filtrate  from  the  iron  and  alumina 
is  treated  with  ammonium  oxalate  (50  c.c.  is  sufficient 
for  1  gram  of  calcium  pigment).     Set  aside  in  a  warm 
place  for  two  or  three  hours,  filter,  ignite,  and  weigh  as 
calcium  oxide,  or  titrate  with  standard  permanganate, 
as  may  be  desired.     The  calcium  may  have  been  present 
as  carbonate  or  sulphate  or  both.     Hence  an  estima- 
tion of  the  sulphur  trioxide  present  in  the  original  sample 
is  necessary.     For  this  purpose  1  gram  is  dissolved  in 
30  c.c.  of  strong  hydrochloric  acid,  boiled  10  minutes, 
diluted  with  50  c.c.  of  water,  heated  to  boiling,  filtered, 
and  washed  with  hot  water.     Neutralize  the  filtrate 
with  ammonia,  then  make  just  distinctly  acid  with 
hydrochloric  acid,  boil,  add  10  c.c.  of  barium  chloride 
solution,  continue  boiling  for  10  minutes,  filter,  wash, 
ignite,  and  weigh  as  barium  sulphate.     Calculate  sul- 
phur trioxide  by  multiplying  weight  of  precipitate  by 
0.343. 

Calculate  the  sulphur  trioxide  found  to  calcium  sul- 
phate and  the  remaining  calcium  to  oxide,  provided 
that  the  carbon  dioxide  is  included  under  loss  on  igni- 
tion. If  desired,  the  remaining  calcium  may  be  cal- 
culated to  calcium  carbonate,  the  combined  carbon 
dioxide  being  deducted  from  the  loss  on  ignition. 

378.  Magnesium.     If  a  considerable  percentage  of  cal- 
cium is  found,  magnesium  is  liable  to  be  present ;  precipi- 
tate with  sodium  hydrogen  phosphate  in  usual  manner. 
Calculate  the  pyrophosphate  to  oxide  by  multiplying 
by  the  factor  0.3624. 


ANALYSIS  OF  INDIAN  REDS,  ETC. 


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180  PAINT  AND  VARNISH  PRODUCTS. 

380.  Tuscan  reds  should  contain  about  60  per  cent 
ferric  oxide,  and  are  often  brightened  up  by  having 
precipitated  on  them  an  organic  red.  Another  class  of 
oxides,  carrying  about  the  same  amount  of  iron  oxide 
as  Tuscan  reds,  is  "  Prince's  metallic/'  The  variation 
of  iron  content  is  shown  in  the  following  analyses: 

No.  Ferric  Oxide. 

I.  44.07 

II  38.17        . 

Ill 68.45 

IV 49.58 

V 39.35 

A  complete  analysis  gave  the  following: 

Per  cent. 

Volatile 3.33 

Ferric  oxide 40 . 91 

Alumina 3.49 

Calcium  oxide 2.00 

Insoluble 49.57 

Undetermined .  0.70 


100.00 

381.  Ochres,  of  which  the  French  ochres  are  consid- 
ered the  best,  to  pass  inspection  by  the  various  service 
department  scientists  of  the  United  States  Government, 
must  be  of  good  bright  color,  contain  at  least  20  per  cent 
sesquioxide  of  iron  and  not  over  5  per  cent  of  lime  in 
any  form.  A  good  grade  of  yellow  ochre  to  pass  this 
inspection  would  analyze  about  as  follows: 

Per  cent. 

Silica 52.14 

Alumina 12.89 

Ferric  oxide 22.42 

Calcium  oxide 0.36 

Combined  water 10.16 

Hygroscopic  water 2 . 03 

100.00 


ANALYSIS  OF  INDIAN  REDS,  ETC. 


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182  PAINT  AND  VARNISH  PRODUCTS. 


Specifications  for  Venetian  Red. 

(Bureau  of  Supplies  and  Accounts,  Navy  Department,  1902.) 

383.  Red,  Venetian.     I.  Red,  Venetian  (bright).    The 
dry  pigment  must  contain  at  least  20  per  cent  of  sesqui- 
oxide  of  iron,  not  more  than  15  per  cent  of  silica,  the 
balance  to  consist  of  sulphate  of  lime  that  has  been  fully 
dehydrated  by  dead  burning,  and  rendered  incapable  of 
taking  up  water  of  crystallization. 

II.  Red,  Venetian  (deep).     The  dry  pigment  must 
contain  at  least  30  per  cent  of  sesquioxide  of  iron,  not 
more  than  15  per  cent  of  silica,  the  balance  to  consist  of 
sulphate  of  lime  that  has  been  fully  dehydrated  by  dead 
burning  and  rendered  incapable  of  taking  up  water  of 
crystallization. 

III.  Red,   Venetian   (medium).     The  dry  pigment 
must  contain  at  least  40  per  cent  of  sesquioxide  of  iron, 
not  more  than  15  per  cent  of  silica,  the  balance  to  con- 
sist of  sulphate  of  lime  that  has  been  fully  dehydrated 
by  dead  burning  and  rendered  incapable  of  taking  up 
water  of  crystallization. 

384.  Priming  ochres.     A  few  years  ago  the  adultera- 
tion of  priming  ochres,  so  called,  was  exceedingly  wide- 
spread.    Paint  legislation  has  done  much  to  check  this 
evil,  and  in  such  states  as  require  the  label  to  show  the 
ingredients  and  percentages  thereof,  the  sale  of  this 
class  of  goods  has  largely  diminished,  and  the  author 
believes  very  few  property  owners  would  care  to  use 
the  cheap  combination  priming  ochres  with  which  the 
market  is  flooded.     It  is  just  as  useless  to  expect  the 
coats  of  paint  applied  over  such  primers  to  give  a 
satisfactory  service  value  as  it  is  to  expect  a  house  to 
stand,  built  on  a  foundation  of  rubbish. 


ANALYSIS  OF  INDIAN  REDS,  ETC.  183 

385.  Analysis.    The  analysis  of  this  class  of  goods 
may  be  performed  substantially  as  described  in  this 
chapter.     The  vehicle  should  receive  careful  examina- 
tion, as  these  so-called  ochres  are  often  ground  in  par- 
affin oil,  low-grade  linseed  oil  containing  large  quanti- 
ties of  foots,  or  in  soya-bean  oil.     The  names  under 
which  such  goods  are  placed  on  the  market  are  also 
misleading,  as  white  ochre,  stone  ochre,  etc.     The  nature 
of  some  of  these  products  is  indicated  by  the  following 

analyses : 

i. 

Per  cent. 

Barium  sulphate 36.24 

Calcium  carbonate 47 . 79 

Aluminum  silicate  and  silica 3 . 87 

Iron  oxide 

Linseed  oil 12.10 

Naphtha 

100.00        100.00 
i  Ochre. 

386.  Tinting  ochres.     Under  this  head  are  included 
pure  French  ochres  ground  in  linseed  oil,  ochres  which 
have  precipitated  on  them  a  small  percentage  of  chrome 
yellow,  and  various  mixtures  of  ochre,  chrome  yellow 
and  inert  pigments  like  barytes,  white  mineral  primer, 
etc.     When  toned  up  with  chrome  yellow,  these  various 
combinations  are  sold  under  some  such  name  as  golden 
ochre,  topaz  ochre,  etc.     The  following  analyses  calcu- 
lated to  formula  indicate  the  nature  of  some  of  these 

combinations : 

i.  n. 

Per  cent.  Per  cent. 

Ochre 63.58  40.60 

Chrome  yellow 2.13  8.91 

Barytes 7.69 

Gypsum 34.29  ... 

Calcium  carbonate 42 . 80 


100.00        100.00 


184  PAINT  AND  VARNISH  PRODUCTS. 

387.  Domestic  ochres.  It  has  been  stated  that  the  use 
of  cheap  domestic  ochres,  of  low  tinting  strength,  fur- 
nished a  ready  means  of  cheapening  mixed  paints  in 
which  yellow  tinting  colors  were  required,  by  the  intro- 
duction of  a  large  amount  of  inert  material  along  with 
the  color.  This  condition  of  affairs  the  author  believes 
to  be  very  improbable,  as  the  color  value  of  the  domes- 
tic ochres  is  very  unlike  the  accepted  grades  of  French 
ochres,  in  that  they  do  not  produce  clean,  clear  tints 
or  give  pleasing  effects,  and  therefore  the  bother  and 
trouble  in  handling  domestic  ochres  is  of  greater  moment 
than  the  difference  in  price. 


CHAPTER  XXI. 

ANALYSIS   OF  BLACK  PIGMENTS  AND   PAINTS. 

388.  Composition.  The  ordinary  black  pigments  — 
lampblack,  vegetable  black,  bone  black,  ivory  drop 
black,  gas  black,  graphite,  etc.  —  contain  carbon  as  their 
essential  constituent,  and  while  all  of  these  products 
are  said  to  be  of  a  black  color,  they  vary  greatly  in 
shade  and  still  more  so  in  tinting  strength. 

1.  Lampblack  and  vegetable  black  are  essentially 
soot  blacks,  being  the  soot  deposited  from  the  combus- 
tion of  oily  bodies  such  as  dead  oil.     Lampblack  has  a 
distinct  gray  tint,  as  may  be  shown  by  comparison  with 
ivory  black.     These  blacks  are  apt  to  contain  varying 
quantities  of  oil,  owing  to  the  nature  of  their  manu- 
facture; less  than  1  per  cent  of  oil  often  being  suffi- 
cient to  retard  seriously  the  drying  of  lampblack  paints. 
Vegetable  blacks  are  more  voluminous  than  lampblacks 
and  are  usually  of  a  jet  black  color. 

2.  Carbon  black  is  usually  produced  from  the  in- 
complete combustion  of  natural  gas.     While  its  tinting 
power  is  very  great,  its  use  has  been  largely  abandoned 
owing  to  its  tendency  to  produce  a  streaky  color  when 
used  in  tinting  paints. 

3.  Bone  black  is,  as  its  name  indicates,  obtained  by 
the  charring  of  bones  in  retorts.     The  carbon  content 
varies  usually  between  12  and  22  per  cent,  the  balance 
consisting  of  moisture,  phosphate  of  calcium,  and  car- 
bonate of  calcium.     The  best  grades  of  bone  black 
are  made  from  selected  sheep  bones.    An  exceedingly 

185 


186  PAINT  AND  VARNISH  PRODUCTS. 

intense  black  is  made  by  digesting  selected  bones  in 
hydrochloric  acid  until  all  of  the  mineral  matter  is  dis- 
solved, leaving  the  carbon  in  a  flocculent  state.  This 
black  is  often  sold  under  the  name  of  black  toner,  and 
is  one  of  the  highest  priced  blacks. 

4.  Animal  black  is  a  name  sometimes  given  to  bone 
black  but  is  also  used  to  designate  a  wide  variety  of 
blacks  prepared  in  the  same  way  as  bone  black  from 
waste  animal  products  of  all  kinds,  as  leather  scrap 
parings,  horn  trimmings,  etc. 

5.  Frankfort  black,  drop  black,  and  German  black 
are  terms  used  to  designate  blacks  made  from  a  variety 
of  organic  materials,  such  as  vine  twigs,  refuse  of  wine 
making,    peach    stones,    bone    shavings,    etc.      These 
blacks  vary  in  hue  from  a  bluish  black  to  a  reddish 
black. 

6.  Graphite,  while  not  used  to  any  extent  in  house 
paints,  is  largely  used  in  bridge,  elevator,  and  warehouse 
paints.     It  is  rarely  used  by  itself  for  these  purposes, 
silica,  calcium  carbonate  and  iron  oxide  pigments,  zinc' 
and  lead  being  the  other  usual  constituents.     It  may 
be  tested  qualitatively  in  the  extracted  pigment  by 
rubbing  a  portion  of  the  sample  between  the  palms, 
which  soon  assume  the  characteristic  appearance  pro- 
duced by  stove  polish.     Of  all  the  black  pigments 
graphite  alone  gives  this  test. 

7.  Charcoal  black  and  vine  black  are  produced  by 
the  charring  of  wood  products,   and  contain  besides 
carbon  the  ash  ingredients  common  to  wood.     Char- 
coal blacks  are  usually  made  from  maple,  willow,  and 
basswood,  and  vine  blacks  from  the  charring  of  the 
grapevine.     Paints  containing  considerable  quantities 
of  these  blacks  are  liable  to  saponify  badly  owing  to  the 
moisture  and  potash  salts  present. 


ANALYSIS  OF  BLACK  PIGMENTS  AND  PAINTS.     187 

8.   Mineral  black,  which  is  still  occasionally  used,  is 
black  slate  finely  ground. 

389.  Moisture.     Dry  2  grams  at  105°  C.  for  3  hours. 
Loss  in  weight  represents  approximately  the  amount  of 
moisture  present. 

390.  Oils.    Extract  2  grams  with  ether  in  a  fat  extrac- 
tion apparatus.     After  removing  the  ether  and  drying, 
any  increase  in  weight  represents  the  amount  of  oily 
matter  present. 

391.  Ash.     Two  grams  are  weighed  into  a  crucible 
and  heated  over  a  Bunsen  burner  until  all  the  carbon 
is  burned  off.     If  the  ash  constitutes  only  a  small  per 
cent,  it  may  be  cooled  and  weighed  directly.     Other- 
wise the  residue  is  moistened  with  a  solution  of  ammo- 
nium  carbonate,   heated   gently,   and  weighed.     The 
object  of  this  operation  is  to  restore  the  carbon  dioxide 
which  may  have  been  expelled  from  the  bases  by  the 
strong  heat  to  which  they  have  been  subjected. 

392.  Carbon.     The  carbon  is  usually  estimated  by  dif- 
ference, by  adding  together  the  moisture,  oil,  and  ash, 
and  subtracting  from  100. 

393.  Calcium.     Digest  the  residue  from  391  in  a  mix- 
ture of  25  c.c.  of  concentrated  hydrochloric  acid  and 
5  c.c.  of  concentrated  nitric  acid  on  the  hot  plate  for 
one-half  hour,  dilute,  filter,  and  make  up  to  250  c.c.  in 
a  graduated  flask.     Any  appreciable  residue  on  the 
filter  may  indicate  addition  of  barytes,  silica,  clay,  or 
alumina.     Determine  the  calcium  and  magnesium  in  an 
aliquot  portion  of  the  solution  by  adding  ammonia  in 
small  quantities  until  a  precipitate  is  formed,   then 
acetic  acid  in  excess  until  redissolved,  except  for  traces 
of  iron  which  may  be  removed  by  filtration.     Ammo- 
nium oxalate  is  added,  and  the  calcium  precipitate 
treated  in  the  usual  manner. 


188  PAINT  AND  VARNISH  PRODUCTS. 

394.  Phosphoric  acid.     Take  an  aliquot  portion  of  the 
solution  prepared  above,  neutralize  with  ammonia,  and 
clear  with  a  few  drops  of  nitric  acid,  add  about  5  grams 
of  dry  ammonium  nitrate  or  a  solution  containing  that 
amount.     To  the  hot  solution  add  50  c.c.  of  molybdic 
solution  for  every  decigram  of  phosphoric  acid  that  is 
present.     Digest  at  about  65°  for  an  hour,  filter,  and 
wash  with  cold  water,  or  preferably  ammonium  nitrate 
solution.     Test  the  filtrate  for  phosphoric   acid    by 
renewed  digestion  and  addition  of  more  molybdic  solu- 
tion.    Dissolve  the  precipitate  on  the  filter  with  am- 
monia and  hot  water,  and  wash  into  a  beaker  to  a  bulk 
of  not  more   than   100   c.c.     Nearly  neutralize  with 
hydrochloric  acid,  and  add  magnesia  mixture  from  a 
burette;  add  slowly  (about  1  drop  per  second),  stirring 
vigorously.     After  15  minutes  add  30  c.c.  of  ammonia 
solution  of  density  0.96.     Let  stand  for  some  time; 
2  hours  is  usually  enough.     Filter,  wash  with  2.5  per 
cent  ammonia,   ignite  to  whiteness  or  to   a  grayish 
white,  and  weigh  as  magnesium  pyrophosphate. 

395.  Preparation  of  reagents.    Molybdic  solution.    Dis- 
solve 100  grams  of  molybdic  acid  in  400  grams  or 
417  c.c.  of  ammonia,  specific  gravity  0.96,  and  pour  the 
solution  thus  obtained  into  1500  grams  or  1250  c.c.  of 
nitric  acid,  specific  gravity  1.20.     Keep  the  mixture  in 
a  warm  place  for  several  days,  or  until  a  portion  heated 
to  40°   deposits  no   yellow  precipitate.     Decant    the 
solution  from  any  sediment  and  preserve  it  in  glass- 
stoppered  vessels. 

Magnesia  Mixture.  Dissolve  110  grams  of  crystal- 
lized magnesium  chloride,  280  grams  of  ammonium 
chloride,  in  700  c.c.  of  ammonia  of  specific  gravity  0.96, 
and  sufficient  water  to  make  2000  c.c. 

396.  Magnesium.    The  filtrate,  from  which  the  cal- 


ANALYSIS  OF  BLACK  PIGMENTS  AND  PAINTS.     189 

cium  has  been  precipitated,  is  evaporated  to  a  small 
bulk  and  made  alkaline  with  ammonia.  After  stand- 
ing several  hours  tlie  magnesium  precipitate  is  filtered, 
ignited,  and  weighed,  and  calculated  to  magnesium  by 
multiplying  by  21.88. 

397.  Calculations.     The  magnesium  is  calculated   to 
magnesium  phosphate,  and  the  remainder  of  the  phos- 
phoric acid  to  calcium  phosphate.     Any  calcium  re- 
maining is  calculated  to  calcium  carbonate. 

Genuine  ivory  black,  made  by  carbonizing  waste  frag- 
ments and  turnings  of  ivory,  is  often  adulterated  with 
bone  black,  which  is  somewhat  similar  in  composition, 
but  contains  only  a  small  amount  of  magnesium  phos- 
phate as  compared  with  the  ivory  black. 

398.  Specifications  for   drop   black.     (Navy  Depart- 
ment, May,  1903.)     Drop  black  must  be  of  good  deep 
luster  and  consist  of  calcined  bone  black  only.     The 
addition  of  blue  or  gas  carbon  black  will  be  ground  for 
rejection.    The  paste  must  contain  not  less  than  45 
per  cent  of  pure  pigment. 

The  pigment  must  be  of  the  best  quality,  free  from 
all  adulterants,  and  equal  in  all  respects  to  the  standard 
sample. 

The  paste  must  be  ground  in  pure  raw  linseed  oil 
only,  to  a  medium  stiff  paste,  which  will  break  up 
readily  in  thinning. 

399.  Specifications   for  carbon  black,  etc.     (Treasury 
Department,  1907.)     Carbon  black  must  be  pure  gas 
carbon  with  not  more  than  0.5  per  cent  of  ash,  that  is, 
97.5  per  cent  of  pure  carbon  and  the  balance  moisture, 
ash,  etc. 

Hard  black;  should  be  suitable  for  making  the  high- 
est class  of  plate  printing  inks;  and  other  factors  being 
equal,  a  color  having  chemical  and  physical  properties 


190  PAINT  AND  VARNISH  PRODUCTS. 

adapted  for  that  purpose  and  which  produces  an  ink 
having  the  most  satisfactory  working  qualities  will  be 
selected.  The  black  now  in  use  has  the  following 
chemical  analysis: 

Per  cent. 

Ash 48.3 

Moisture 3.7 

Carbon 48.0 

Ash  insoluble  in  hydrochloric  acid  11.4  per  cent. 

Soft  Black.     Requirements  same  as  for  hard  black. 
The  black  in  use  has  the  following  chemical  analysis: 

Per  cent. 

Ash 56.1 

Moisture 2.5 

Carbon  (by  diff.) 41.4 


100.0 

Ash  insoluble  in  hydrochloric  acid  36.3  per  cent. 

400.   COMPOSITION  OF  IVORY  AND  BONE. 
IVORY  (Uncakined). 

I.  II. 

Per  cent.  Per  cent. 
Calcium  phosphate,  including  slight 

amount  of  calcium  fluoride 38 . 48  46 . 48 

Calcium  carbonate 5 . 63            3 . 86 

Magnesium  phosphate 12.01            7.84 

Soluble  salts 0.70            0.77 

Organic  matter 43.18  41.05 


100.00  100.00 

BONE  (Uncakined'). 

I.  II. 

Per  cent.  Per  cent. 

Calcium  phosphate 61.4  62 . 4 

Calcium  carbonate 8.6  7.9 

Magnesium  phosphate 1.7  1.7 

Organic  matter 28 . 3  28 . 0 

100.0  100.0 


ANALYSIS  OF  BLACK  PIGMENTS  AND  PAINTS.     191 


401. 


TYPICAL  ANALYSES  BY  THE  AUTHOR  OF  THE 
VARIOUS  BLACKS. 


I. 

II. 

III. 

Ivory  Drop 

Lamp- 

Lamp- 

Black. 

black. 

black. 

Per  cent. 

Per  cent. 

Per  cent. 

^Moisture        

0.14 

2.24 

2.18 

Oil                  ..... 

0.22 

0.35 

0.19 

Ash                     .... 

15.23 

0.32 

0.10 

84.41 

97.09 

97.53 

100.00 

100.00 

100.00 

I. 

II. 

III. 

Ivory                    German  Ivory 
Black.i                          Black. 

Ivory 
Black.i 

Per  cent. 

Per  cent. 

Per  cent. 

0.75 

2.33 

2.59 

0.17 

0.22 

0.14 

88  98 

84.82 

84.70 

isoluble    ....     0.88 

0.42 

0 

.32 

alcium  phosphate  73.72 

77.51 

77 

.82 

alcium  carbonate  14.00 

6.51 

5 

.60 

Oil 
Ash 

Ii 

C 

C 

Magnesium    phos- 
phate   0.38 

Carbon   . 


0.38 


10.10 


12.63 


0.96 


100.00  100.00 

1  Not  true  ivory  blacks. 


12.57 
100.00 


Analysis  of  Mixed  Paints  Tinted  with  Black  and  Oxide 
of  Iron  Pigments. 

402.  Carbon.     One  gram  of  the  pigment  is  dissolved 
in  hydrochloric  acid  as  described  under  white  pigments, 
and  the  residue  filtered  through  an  ashless  filter,  that  has 
been  dried  in  the  hot- water  oven  and  weighed.     After 
washing  the  residue  with  boiling  water  the  filter  and 
contents  are  dried  and  weighed,  then  ignited  until  all 
the  carbon  is  burned  off,  and  weighed  again.     The  per- 
centage of  carbon  is  obtained  by  difference.     Where 
the  percentage  of  color  is  small,  it  is  often  estimated  by 
difference,  adding  together  the  determined  constituents 
and  subtracting  from  100. 

403.  Ferric  oxide.     If  the  filtrate  from  the  insoluble 


192  PAINT  AND  VARNISH  PRODUCTS. 

residue  is  of  an  appreciable  yellow  color,  it  indicates 
that  the  tint  has  been  " warmed  up"  by  the  addition  of 
an  ochre  or  oxide,  in  which  case  the  lead  is  precipi- 
tated and  estimated  as  described  under  analysis  of 
white  pigments,  the  nitrate  from  the  lead  sulphide 
heated  until  all  of  the  hydrogen  sulphide  has  been 
expelled  and  the  iron  and  alumina  precipitated  with 
ammonia  after  having  been  oxidized  by  boiling  with  a 
few  drops  of  nitric  acid,  filtered  and  ignited  and  weighed 
in  a  porcelain  crucible,  the  residue  fused  with  bisul- 
phate  of  potassium,  dissolved  in  water  with  the  aid 
of  a  little  hydrochloric  acid,  heated  to  boiling,  reduced 
with  stannous  chloride;  mercuric  chloride  and  man- 
ganous  sulphate  solution  added  and  titrated  with  per- 
manganate in  the  manner  described  under  analysis  of 
Venetian  reds. 

404.  Alumina.    The  alumina  is  calculated  by  differ- 
ence from  the  data  obtained  under  403. 

405.  Zinc  oxide.     The  filtrate  from  the  iron  and  alu- 
mina precipitate  and  the  nitrate  from  the  lead  sulphate 
precipitate,  the  alcohol  having  been  removed  by  evap- 
oration, are  mixed,  made  distinctly  alkaline  with  ammo- 
nia, and  the  zinc  precipitated  with  hydrogen  sulphide. 
The  liquid  containing  the  zinc  sulphide  precipitate  is 
heated  to  boiling,  and  about  5  grams  of  solid  ammo- 
nium chloride  added,   which  renders  the  precipitate 
easier  to  filter.     Settle,  filter,  and  wash  thoroughly. 
Pierce  filter,  wash  through  into  a  clean  beaker  with 
water,  dissolving  the  residue  on  filter  with  dilute  hydro- 
chloric acid,  and  wash  with  hot  water.     Dilute,  heat  to 
expel  hydrogen  sulphide,  and  titrate  with  'ferrocyanide 
as  previously  described.     If  iron  is  absent  in  the  paint 
the  zinc  may  be  estimated  directly  as  described  under 
analysis  of  white  paints. 


ANALYSIS  OF  BLACK  PIGMENTS  AND  PAINTS.      193 

406.  Calcium  and  magnesium.    Estimate  as  usual  in 
the  filtrate  from  the  zinc  sulphide. 

407.  Residue  insoluble  in  hydrochloric  acid.     Fuse  with 
sodium  carbonate  as  previously  described.     Dissolve  in 
water  and  filter.     Iron  not  previously  dissolved  will 
remain  on  the  filter  as  ferric  oxide  along  with  any 
barium  that  may  be  present.     This  residue  after  thor- 
ough washing  is  dissolved  with  the  aid  of  a  small 
quantity  of  hydrochloric  acid,  the  barium  precipitated 
as  usual,  and  the  iron  estimated  in  the  filtrate  from  the 
barium  sulphate.     The  silica  and  alumina  are  estimated 
as  usual. 

408.  Lead   sulphate.     Determine   the   combined   sul- 
phuric acid  as  described  under  analysis  of  white  paints 
and  calculate  to  lead  sulphate  in  the  absence  of  calcium 
sulphate.     If  calcium  carbonate  and  calcium  sulphate 
are   both   present   the  nitric  acid-alcohol    separation 
should  be  used. 


409.   ANALYSES,   BY  AUTHOR,   OF  PAINTS  TINTED  WITH 
BLACKS,   OCHRE,  AND  IRON  OXIDES. 

I.  II. 

Light  Drab.          Drab. 

Net  weight 61bs.  6oz.  Gibs.  12 oz. 

Capacity  of  can,  qts 2.06  2.03 

Contents,  qts 1.93  1.92 

Per  cent.          Per  cent. 

-       Pigment  by  weight 56.6  56.9 

'  Vehicle 43.4  43.1 


100.00  100.00 
ANALYSIS  OF  VEHICLE. 

Per  cent.  Per  cent. 

Linseed  oil     .    .    . 92.9  92.0 

Turpentine  drier 7.0  6.2 

Water 0.1  1.8 

100.0  100.0 


194  PAINT  AND  VARNISH  PRODUCTS. 

ANALYSIS  OF  PIGMENT. 

Per  cent.  Per  cent. 

White  lead 26.57                 27.73 

Lead  sulphate 0 . 78                    2 . 39 

Zinc  oxide 62.34                  57.12 

Color 10.31                  12.76 

Clay  and  silica 5.56                    7.74 

Iron  oxide 3 . 02                    3 . 89 

Carbon  and  undetermined  .  1 . 73                    1.13 


100.00  100.00 

410.  Graphite  paints.    The  term  graphite  as  applied  to 
paints  does  not  necessarily  mean  that  such  paints  are 
composed  of  graphite  wholly  or  even  in  part.     In  fact 
there  is  no  accepted  standard  of  purity  for  graphite 
itself.     One  paint  manufacturer  may  purchase  a  nat- 
ural graphite  for  his  line  of  graphite  paints  which  con- 
tains 20  per  cent  of  graphitic  carbon,  the  other  80  per 
cent  being  silica  and  various  silicates;  others  may  pur- 
chase graphites  containing  80  per  cent  or  more  of  graph- 
itic carbon ;  and  some  purchase  products  which  are  very 
nearly   pure   graphitic   carbon,    prepared   electrically. 
While  it  is  a  far  from  settled  question,  perhaps  the 
majority  of  paint  manufacturers  and  those  who  buy 
graphite  paints  under  strict  specifications  are  of  the 
opinion  that  a  graphite  paint  affords  better  service 
value   when   it    contains,  in   part    something   besides 
graphitic  carbon. 

411.  Colored  graphite  paints.     Having  established  his 
graphite  paint  on  the  market,  the  manufacturer  soon 
has  requests  for  colors  other  than  black,  and  in  order 
to  meet  the  requirements  of  his  trade  he  finds  it  neces- 
sary to  add  considerable  amounts  of  tinting  pigments, 
with  the  natural  result  that  in  time  many  of  his  formulas 
contain  little  or  no  graphite. 

412.  The  following  analyses  will  give  some  idea  of 
the  pigment  combinations  to  be  found  on  the  market: 


ANALYSIS  OF  BLACK  PIGMENTS  AND  PAINTS.      195 

I.                 II.              ill.  IV. 

Natural              Olive              Indian  Seal 

Graphite.         Graphite.             Red  Brown 

Graphite.  Graphite. 

Per  cent.          Per  cent.          Per  cent.  Per  cent. 

Graphitic  carbon 32.14          21.89            ...  5.31 

Calcium  carbonate   ....       42.86           19.16          44.59  26.12 
Magnesium  silicate  and  sili- 
cate        25.00            ...              12.17  33.72 

Ochre 58.95 

Ferric  oxide   .                                ...                ...              43.24  34.85 


100.00         100.00         100.00         100.00 


The  pigment  portion  of  one  sample  analyzed  by  the 
author  was  nothing  but  Keystone  filler;  another,  carbon 
black,  which  while  as  expensive  as  the  ordinary  grades 
of  graphite  is  nevertheless  radically  different.  Graphite 
paints  which  are  sold  according  to  specifications  for 
structural  iron  and  steel  work  are  usually  high-grade 
products. 


CHAPTER  XXII. 

ANALYSIS   OF  BROWN  PIGMENTS  AND  PAINTS. 

Vandyke-brown.     Composition. 

413.  Vandyke-browns  vary   widely  in  composition 
according  to  the  method  of  preparation.     Some  are 
obtained  from  natural  deposits  of  an  organic  nature, 
such  as  peat,  decayed  vegetable  matter,  etc. ;  or  by  the 
slight  calcining  of  cork  cuttings,  bark,  and  twigs  of  trees; 
while  some  of  the  more  common  varieties  are  prepared 
by  mixing  lampblack  or  other  black  pigments  with 
sufficient  red  oxide  and  ochre  to  give  the  desired  shade. 

414.  Analyses  of  two  Vandyke-browns  by  the  author 
gave  the  following  results : 

i.  IT. 

Organic  matter  and  moisture     ....  90.95  91.10 

Ash 9.05  8.90 

Silica 1.90  2.61 

Alumina  and  ferric  oxide 1 . 43  1 . 50 

Calcium  carbonate 4.98  3.28 

Soluble  salts 0.74  1.51 


100.00  100.00 

Analysis  of  Umbers  and  Siennas. 

415.  Hygroscopic  moisture.     Heat  2  grams  at  105°  C. 
for  3  hours.     Loss  in  weight  represents  hygroscopic 
moisture. 

416.  Combined  water.     Transfer  above  sample  to  a 
weighed  platinum  crucible  and  heat  for  1  hour  over  an 
ordinary  lamp,  or  better  in  a  muffle.     Loss  in  weight 
indicates  amount  of  combined  water.     Carbonates  and 


ANALYSIS  OF  BROWN  PIGMENTS  AND  PAINTS.      197 

organic  matter  render  the  results  inaccurate,  in  which 
case  continue  the  ignition  at  bright  red  heat  for  several 
hours,  and  weigh  again.  Determine  the  carbon  dioxide 
in  another  portion  of  the  sample  and  estimate  the  com- 
bined water  by  difference. 

417.  Silica  and  barium  sulphate.     One  gram  of  the  pig- 
ment is  intimately  mixed  with  6  to  8  grams  of  potassium 
bisulphate  and  fused  in  a  large  porcelain  crucible,  the 
cover  of  which  is  small  enough  to  set  inside  the  top  of 
the  crucible,  at  not  too  high  a  temperature  for  one- 
half  hour;  finally  heating  the  side  of  the  crucible  to 
finish  the  conversion  of  any  material  adhering  to  the 
cover  and  upper  portion  of  the  crucible.     The  iron, 
manganese,   aluminum,   calcium,   and  magnesium  are 
converted   into   sulphates,    the   barytes   remains   un- 
changed, and  the  silica  is  completely  dehydrated. 

After  cooling,  the  entire  contents  of  the  crucible  may 
be  shaken  loose  and  dissolved  in  sufficient  water  and  a 
little  hydrochloric  acid.  Filter  and  make  up  to  250  c.c. 

418.  The  residue  remaining  on  the  filter,  which  should 
be  white,  a  red  or  brownish  color  indicating  incomplete 
fusion  with  potassium  bisulphate,  in  which  case  the 
sample  must  be  fused  again,  is  ignited,  and  weighed  in 
a  platinum  crucible.     The  residue  is  tested  for  barium 
sulphate  by  the  flame  test:  if  absent,  the  residue  is 
reported  as  silica;  if  present,  the  residue  is  treated  in 
the  crucible  with  hydrofluoric  acid  until  a  thin  paste  is 
formed.     The  mixture  is  stirred  with  a  platinum  wire 
and  digested  at  a  gentle  heat;  finally  two  or  three  drops 
of  sulphuric  acid  are  added  and  the  temperature  gradu- 
ally raised  until  no  further  loss  in  weight  takes  place, 
indicating  that  the  silica  has  been  completely  expelled. 
The  residue  is  weighed  as  barium  sulphate  and  the  loss 
in  weight  represents  the  silica. 


198  PAINT  AND  VARNISH  PRODUCTS. 

419.  Ferric  oxide.    An  aliquot  portion  of  the  solution 
from  417  is  heated  nearly  to  boiling  and  stannous  chlo- 
ride solution  added  cautiously  until  the  yellow  color  has 
disappeared,  and  then  a  slight  excess  added.     All  at 
once  with  vigorous  shaking  of  the  flask  50  c.c.  of  mer- 
curic chloride  solution  is  added,  then  50  c.c.  of  the 
manganous  sulphate  solution.     Dilute  with  cold  fresh- 
boiled  water  and  titrate  with  permanganate  solution. 
Calculate  iron  found  to  ferric  oxide. 

420.  Manganese.    Digest  0.5  gram  of  the  sample  with 
15  c.c.  of  concentrated  hydrochloric  acid  until  all  of  the 
iron  and  manganese  has  dissolved,  then  add  5  c.c.  of 
sulphuric  acid  diluted  with  10  c.c.  of  water,  and  evapo- 
rate on  the  hot  plate  until  all  of  the  hydrochloric  acid  is 
expelled  as  shown  by  copious  evolution  of  sulphur  tri- 
oxide  fumes.     Cool,  dissolve  in  about  25  c.c.  of  water, 
and  heat  carefully  with  occasional  shaking  until  all  of 
the  anhydrous  sulphate  of  iron  has  dissolved.     Trans- 
fer to  a  250  c.c.  graduated  flask  and  add  an  excess  of 
zinc  oxide  emulsion,  obtained  by  mixing  C.  P.  zinc 
oxide  with  water.    Avoid  a  large  excess,  but  sufficient  to 
precipitate  all  the  iron,  so  that  on  standing  the  solution 
begins  to  settle  clear  and  some  zinc  oxide  can  be  seen  in 
the  bottom  of  the  flask.    Cool  and  make  up  to  the  mark. 

421.  Transfer  an  aliquot  portion  to  a  beaker  or  flask, 
and  add  an  excess  of  a  saturated  solution  of  bromine 
water  and  about  3  grams  of  sodium  acetate.     One  c.c. 
of  a  saturated  solution  of  bromine  water  will  precip- 
itate about  0.01  gram  of  manganese.     Boil  for  about 
2  minutes.      Filter  and  wash  with  hot  water.      The 
filtrate  must  be  perfectly  clear.     Place  the  filter  con- 
taining the  washed  precipitate  back  in  the  beaker  or 
flask  in  which  the  precipitation  was  made.      All  traces 
of  bromine  must  be  entirely  expelled. 


ANALYSIS  OF  BROWN  PIGMENTS  AND  PAINTS.      199 

422.  Add  an  excess  of  standard  oxalic  acid  solution 
and  about  50  c.c.  of  dilute  sulphuric  acid  (1:9)  and 
heat  nearly  to  boiling  with  gentle  agitation  until  the 
precipitate  is  entirely  dissolved.     Dilute  to  about  200 
c.c.  with  hot  water,  and  titrate  with  standard  perman- 
ganate. 

Standard  oxalic  acid  solution.  Dissolve  12.6048  grams 
of  chemically  pure  oxalic  acid  in  freshly  boiled  water  and 
make  to  1000  c.c.  in  a  graduated  flask. 

One  c.c.  of  this  solution  =  .0055  gram  of  manganese. 

The  oxalic  acid  solution  should  be  standardized  against 
the  standard  permanganate  solution  and  the  correction 
factor  calculated. 

Example:  Wt.  of  sample  taken  =  0.5  gram. 

Volume  of  solution     =  250  c.c. 

Aliquot  portion  used  =  100  c.c.  =  0.2  gram. 
1  c.c.  of  permanganate  sol.  =  0 . 499  c.c.  of  oxalic  acid. 
1  c.c.  of  oxalic  acid  sol.  =  0.0055  gram  of  manganese. 

Permanganate  solution  used  in  titrating  excess  of 
oxalic  acid  solution  =  13.2  c.c. 

13.2  c.c.  =6.59  c.c.  of  oxalic  acid. 
Oxalic  acid  solution  used,  10.00  c.c. 

Excess,  6.59  c.c. 

Consumed,  3.41  c.c. 

3.41  x  .0055  =  .018755  g.  Mn. 
Mn:Mn02  :  .  018755  :z. 

x  =  .  02967  g.  Mn02. 
.02967  +  0.2  =  14.84  per  cent  Mn02. 

423.  Alumina.    Fifty  c.c.  of  the  250  c.c.  solution  pre- 
pared in  417  is  treated  with  about  20  grams  of  solid 


200  PAINT  AND  VARNISH  PRODUCTS. 

ammonium  chloride,  made  just  alkaline  with  ammonia, 
heated,  allowed  to  settle,  decanted,  filtered,  and  washed. 
The  precipitate  is  dissolved  on  the  filter  with  hydro- 
chloric acid  and,  after  washing  with  small  portions 
of  boiling  water,  the  iron  and  aluminum  is  repre- 
cipitated,  solid  ammonium  chloride  being  added  as 
before.  The  precipitate  is  washed  by  decantation,  fil- 
tered, and  the  filtrate  collected  in  the  beaker  containing 
the  first  filtrate.  This  treatment  frees  the  iron  and 
aluminum  from  any  manganese  and  the  precipitate  may 
be  dried,  ignited,  and  weighed  in  the  usual  manner,  the 
alumina  being  obtained  by  difference.  It  is  often  ad- 
visable to  make  another  reprecipitation  of  the  iron 
and  alumina,  using  but  a  small  amount  of  ammonium 
chloride. 

424.  Calcium  and  magnesium.  The  combined  filtrates 
from  the  iron  and  alumina  are  treated  with  colorless 
ammonium  sulphide  in  such  a  manner  as  to  form  the 
green  sulphide  of  manganese,  which  is  very  much  easier 
to  filter  than  the  pink  sulphide. 

The  colorless  ammonium  sulphide  may  be  prepared 
as  follows:  Saturate  one-half  of  a  solution  of  100  c.c.  of 
water  and  50  c.c.  of  ammonia  (sp.  gr.  0.90)  with  hydro- 
gen sulphide,  and  then  add  the  other  half  of  the  solu- 
tion. 

For  the  precipitation  of  the  manganese,  25  c.c.  of  the 
ammonium  sulphide  solution  and  10  c.c.  of  ammonium 
chloride  solution  containing  3  grams  of  the  dry  salt  are 
placed  in  an  Erlenmeyer  flask,  the  solution  diluted  to 
about  100  c.c.  and  heated.  As  soon  as  it  comes  to  a 
boil,  the  combined  filtrate  from  the  iron  and  alumina 
is  added  and  the  beaker  rinsed  with  a  little  water. 
The  flask  is  shaken  vigorously  and  the  solution  kept 
nearly  at  the  boiling  point.  After  alternate  shaking 


ANALYSIS  OF  SHOWN  PIGMENTS  AND  PAINTS.     201 

and  heating,  the  pink  sulphide  of  manganese  turns 
green  and  settles  readily,  leaving  a  clear  supernatent 
liquid.  If  the  ammonium  sulphide  is  of  the  proper 
strength  and  a  sufficient  amount  be  used,  there  should 
be  no  difficulty  in  obtaining  the  green  sulphide  in 
proper  condition  for  filtering. 

After  filtering  off  the  manganese,  the  filtrate  is  evap- 
orated to  a  syrupy  consistency  and  20  c.c.  of  nitric 
acid  (sp.  gr.  1.2)  added  in  small  portions,  evaporating 
each  time.  Sufficient  hydrochloric  acid  is  added  and 
heat  applied,  until  the  brown  fumes  cease  to  be  given 
off.  This  treatment,  which  removes  the  excess  of  am- 
monium salts,  is  not  necessary  if  magnesium  is  known 
to  be  absent. 

The  solution,  after  the  removal  of  the  nitric  acid,  is 
diluted  with  water,  made  alkaline  with  ammonia,  and 
the  calcium  and  magnesium  separated  and  estimated 
in  the  usual  manner,  both  being  calculated  to  the 
oxides.  The  calcium  may  have  been  present  as  car- 
bonate or  sulphate  or  both.  Hence  an  estimation  of 
the  combined  sulphuric  acid  present  in  the  original  sam- 
ple is  necessary.  For  this  purpose  1  gram  is  dissolved 
in  30  c.c.  of  strong  hydrochloric  acid  boiled  10  min- 
utes, diluted  with  50  c.c.  of  water  heated  to  boiling, 
filtered,  and  washed  with  hot  water.  Neutralize  the 
filtrate  with  ammonia,  then  make  just  distinctly  acid 
with  hydrochloric  acid,  boil,  add  10  c.c.  of  barium 
chloride  solution,  continue  boiling  for  10  minutes,  filter, 
wash,  ignite,  and  weigh  as  barium  sulphate.  Calculate 
combined  sulphuric  acid  by  multiplying  weight  of  pre- 
cipitate by  0.343. 

Calculate  the  combined  sulphuric  acid  found  to  cal- 
cium sulphate  and  the  remaining  calcium  to  oxide. 


202 


PAINT  AND  VARNISH  PRODUCTS. 


425.  ANALYSES  OF  UMBERS  AND  SIENNAS  BY  THE  AUTHOR. 

I.  ii. 

Raw  Burnt 

Sienna.  Sienna. 

Moisture 0.42  0.44 

Loss  on  ignition    . 12.28  12.67 

Silica 36.85  19.55 

Ferric  oxide 45 . 18  62 . 75 

Alumina 3.00  1.66 

Calcium  oxide 1 . 09  2 . 52 

Magnesium  oxide 0.85  0.00 

Sulphur  trioxide        0.15  0.20 

Manganese  dioxide 0.13  0.17 

Undetermined 0.05  0.04 

100.00  100.00 

III.  IV. 

Raw  Burnt 

Umber.  Umber. 

Moisture 1.78  2.01 

Loss  on  ignition 13.64  3.94 

Silica 20.60  24.21 

Ferric  oxide 42.60  51.04 

Alumina 2.90  6.80 

Calcium  oxide 3.68  1.95 

Magnesium  oxide 2.16 

Sulphur  trioxide 0.36  0.22 

Manganese  dioxide 11.95  9.79 

Undetermined   .                                               0.33  0.04 


100.00 


100.00 


Analysis  of  Mixed  Paints  Containing  Umbers, 
Siennas,  and  Ochres. 

426.  Determine  the  manganese  in  a  separate  sample 
as  determined  under  the  analysis  of  umbers.  Deter- 
mine the  lead  as  in  white  paints,  using  the  filtrate  from 
the  lead  sulphide  for  the  estimating  of  the  iron,  which 
must  be  oxidized  by  boiling  with  a  little  nitric  acid  be- 
fore precipitating.  Determine  aluminum,  zinc,  calcium, 
and  magnesium  as  described  under  analysis  of  umbers 
and  siennas.  The  zinc  being  precipitated  as  the  sul- 
phide after  the  removal  of  the  iron  and  aluminum  is 


ANALYSIS  OF  BROWN  PIGMENTS  AND  PAINTS.      203 

contaminated  with  manganese  sulphide.  Dissolve  the 
mixed  sulphides  in  dilute  hydrochloric  acid,  boil  until 
the  odor  of  hydrogen  sulphide  is  expelled.  Cool.  Add 
excess  of  sodium  hydroxide  and  filter  off  the  precipi- 
tated manganese  hydroxide,  washing  thoroughly.  The 
filtrate  containing  the  zinc  in  solution  as  sodium  zincate 
is  acidified  with  hydrochloric  acid,  heated  to  about 
80°  C.,  and  titrated  with  potassium  ferrocyanide  in  the 
usual  manner. 

Any  barytes,  silica,  and  insoluble  silicates  are  sepa- 
rated and  estimated  as  usual. 


CHAPTER  XXIII. 

ANALYSIS   OF  BLUE  PIGMENTS  AND   PAINTS. 

Analysis  of  Prussian  Blues,  Chinese  Blues,  etc. 

427.  Hygroscopic  moisture.     Heat  2  grams  to  105°  C. 
for  3  hours.     Loss  in  weight  represents  hygroscopic 
moisture. 

428.  Water  of  combination.    The  water  of  combination 
(so    called)  cannot  with    advantage    be    determined 
directly,  but  can  be  approximated  by  subtracting  the 
total   per   cent   of   constituents   determined  —  hygro- 
scopic   moisture,    cyanogen,    iron,    aluminum,    alkali 
metal,  alkaline  sulphate,  and  inert  base,  if  any  —  from 
100  per  cent. 

429.  Iron.     Ignite  1  gram  at  a  temperature  sufficient 
to  decompose  the  last  trace  of  the  blue,  but  not  so 
high  as  to  render  the  oxide  of  iron  difficult  of  solution. 
Dissolve  in  25  c.c.  of  hydrochloric  acid  and  25  c.c.  of 
water  with  aid  of  heat.     Filter,  making  up  filtrate  to 
250  c.c.     Titrate  50  c.c.  with  potassium  permanganate, 
after  adding  stannous  chloride,  mercuric  chloride,  and 
manganous   sulphate  solution  in   the  usual  manner. 
Calculate  to  metallic  iron. 

430.  Aluminum.     Precipitate  the  iron  and  aluminum 
from  50  c.c.  of  the  iron  solution.     Filter,  ignite,  and 
weigh,  estimating  the  alumina  by  difference.     It  prob- 
ably exists  in  the  Prussian  blue  as  aluminum  ferrocy- 
anide.     Calculate  to  metallic  aluminum. 

204 


ANALYSIS  OF  BLUE  PIGMENTS  AND  PAINTS.      205 

431.  Calcium.     Calcium  compounds  are  very  rarely 
found  in  Prussian  blues.     If  the  Prussian  blue  is  pre- 
cipitated on  barytes,  the  latter  is  liable  to  contain  a 
small  amount  of  calcium  carbonate  as  an  impurity. 
Treat  the  filtrate  from  430  with  ammonium  oxalate. 
Settle,  filter,  ignite,  and  weigh  as  calcium  oxide.     Cal- 
culate to  calcium  carbonate. 

432.  Alkali  metal  and  alkaline  salts.     The  filtrate  from 
431  is  evaporated  to  dryness  in  a  weighed  evaporating 
dish,  the  ammonium  salts  completely  volatilized,  the 
alkaline  salts  weighed,  and  the  chlorine  therein  deter- 
mined by  titration  with  standard  silver  nitrate  solution. 
The  alkali  metal  is,  almost  without  exception,  entirely 
sodium  or  potassium  and  not  a  mixture  of  the  two,  and 
may  be  identified  by  the  flame  test,  using  a  small  frag- 
ment of  the  weighed  alkaline  salt.     The  sulphuric  acid 
is  estimated,  in  50  c.c.  of  the  solution,  in  the  usual 
manner.     The  amount  obtained  is  calculated  to  sodium 
sulphate  or  potassium  sulphate,  as  the  case  may  be. 
The   potassium  or  sodium  chemically  combined  with 
the  Prussian  blue  is  calculated  from  the  amount  of 
chlorine  found  and  reported  as  metallic  sodium  or 
potassium. 

433  •  Cyanogen.  Estimate  the  nitrogen  in  1  gram  of 
the  sample  by  the  Kjeldahl-Gunning  method.  Multiply 
the  nitrogen  obtained  by  1.86  to  convert  it  into  cyanogen. 

434.  Barytes,  silica,  clay,  etc.     The  insoluble  portion 
remaining  on  the  filter  paper  in  429  is  ignited  and 
weighed.     Fuse  with  sodium  carbonate  and  estimate 
the  barytes,  silica,  alumina,  etc.,  as  described  under 
analysis  of  white  paints. 

435.  Calculations.     The  amount  of  Prussian  blue  may 
be  calculated  approximately  by  multiplying  the  iron 
content  by  3.03  or  the  nitrogen  content  by  4.4.     These 


206  PAINT  AND  VARNISH  PRODUCTS. 

factors  are  not  exact,  as  Prussian  blues  have  varying 
compositions. 

A  Prussian  blue  to  be  considered  pure  should  contain 
at  least  20  per  cent  of  nitrogen  and  30  per  cent  of  iron 
calculated  on  the  dry  matter  and  after  burning  should 
be  entirely  soluble  in  hydrochloric  acid.  A  dry  blue 
should  contain  less  than  7  per  cent  moisture,  and  the 
sulphuric  acid  in  the  Kjeldahl  nitrogen  determination 
should  not  be  blackened,  which  \vould  indicate  organic 
adulteration. 

436.  ANALYSES  OF   "PURE"   PRUSSIAN  BLUES.1 

I.  II.  III.  IV. 

Moisture  (lost  at  100°  C.)   .  5.61  3.54  5.36  5.45 

Water  of  combination,  etc.  .  15.46  18.18  6.22  13.07 

Cyanogen  37.72  41.10  42.97  37.90 

Iron     29.48  32.16  34.27  30.32 

Aluminum      1.82  .52  ...  3.17 

Alkali  metal  (Na)     ....  7.60  (K)  4.50  (K)  7.72     (K)  2.25 

Alkaline  sulphate      ....  2.31  3.46  7.84 

100.00         100.00         100.00         100.00 

v.  VI.  VII.  vm. 

Moisture  (lost  at  100°  C.)    .       74.53  5.32  5.56  5.61 

Water  of  combination,  etc.  .         3.08  7.86  14.60  16.93 

Cyanogen            10.64  39.91  40.19  40.86 

Iron           7.97  30.94  31.94  31.25 

Aluminum 72  1.00  1.43  1.52 

Alkali  metal  (Na) (K)1.06  (K)ll.31  Na2.52  .76 

Alkaline  sulphate 2.00  3.66  3.76  Na3.07 

100.00        100.00        100.00        100.00 
1  Parry  and  Coste,  The  Analyst,  Vol.  XXL,  page  227. 

437.  ANALYSES  OF  CHINESE  BLUES  BY  AUTHOR. 

I.  II.  in. 

Moisture  (lost  at  100°  C.) 2.49  3.45  2.04 

Water  of  combination,  etc 12.69  18.12  8.75 

Cyanogen  .                   45.78  36.51  46.09 

Iron         35.87  32.34  35.86 

Aluminum      

Alkali  metal Nal.57  (K)4.89  Na3.80 

Alkaline  sulphate 1.50  3.61  3.35 

Silica 0.10  1.08  0.11 

100.00        100.00        100.00 


ANALYSIS  OF   BLUE  PIGMENTS  AND  PAINTS.      207 

Analysis  of  Mixed  Paints  Containing  Prussian  Blue, 
Chinese  Blue,  etc. 

438.  Weigh  1  gram  into  a  250  c.c.  beaker,  add  30  c.c. 
of  concentrated  hydrochloric  acid,  boil  5  minutes,  add 
50  c.c.  of  hot  water,  boil   10  minutes,  filter.     Wash 
thoroughly  with  boiling  water.     Ignite,  filter,  and  pre- 
cipitate gently,  so  as  to  destroy  the  blue  color  but  not 
at  a  sufficiently  high  temperature  to  render  the  iron 
oxide  difficultly  soluble  in  acid.     Cool,  digest  in  moder- 
ately concentrated  hydrochloric  acid  until  the  iron  is 
all  dissolved.     Dilute,  filter,  adding  this  filtrate  to  the 
first  filtrate.     The  insoluble  residue  is  ignited,  weighed, 
and  fused  with  sodium  carbonate,  the  barium,  silica, 
and  alumina  separated  as  described  under  analysis  of 
white  paints.     The  lead,  iron,  soluble  aluminum,  zinc, 
and  any  calcium  and  magnesium  compounds  separated 
and  estimated  as  described  under  analysis  of  mixed 
paints  containing  blacks  and  oxide  of  iron  pigments. 

439.  If  the  paint  in  question  is  free  from  other  iron 
pigments,  the  percentage  of  Prussian  blue  may  be  cal- 
culated by  multiplying  the  iron  content  by  3.03.     If 
other  iron  pigments  are  present  the  nitrogen  content 
must  be  determined;  this  multiplied  by  4.4  will  give  the 
approximate  amount  of  Prussian  blue  present. 

Analysis  of  Ultramarine. 

440.  Properties.     Ultramarine  is  a  compound  of  silica 
containing  alumina,  soda,  sulphur,  and  combined  sul- 
phuric acid.     It  has  been  often  stated  that  ultramarine 
cannot  be  mixed  with  white  lead,  because  of  the  sul- 
phur content  of  the  ultramarine,  but  the  author  has 
ascertained  that   a  great  many  paint  manufacturers 


208  PAINT  AND  VARNISH  PRODUCTS. 

use  it  in  tinting  mixed  paints  where  the  percentage  of 
white  lead  does  not  exceed  that  of  the  zinc,  without  any 
harmful  results  following.  Ultramarines  that  are  to  be 
used  in  the  manufacture  of  paper  should  be  tested  for 
their  power  of  resisting  the  action  of  alum,  by  boiling 
5  grams  in  a  5  per  cent  alum  solution.  As  found  on 
the  market,  ultramarines  vary  much  in  tint,  brilliance, 
and  coloring  power. 

441.  Moisture.     Heat  2  grams  at  1.05°  C.  for  3  hours, 
cool,  and  weigh. 

442.  Silica.     Digest  1  gram  in  a  casserole  provided 
with  a  beaker  cover,  with  30  c.c.  of  concentrated  hydro- 
chloric acid.     Evaporate  to  complete  dryness,  cool,  add 
2  c.c.  of  concentrated  hydrochloric  acid,  evaporate  to 
dryness,  and  heat  gently  for  15  minutes.     Take  up  in 
100  c.c.  of  hot  water,  add  10  c.c.  of  hydrochloric  acid. 
Filter,  ignite,  and  weigh  as  silica. 

443.  Alumina.    The  nitrate  from  the  silica  is  made  just 
sufficiently  alkaline  with  ammonia  to  precipitate  the 
aluminum.      Heat  gently,  filter,  ignite,  and  weigh  as 
alumina. 

444.  Sodium  oxide.     The  filtrate  from  the  alumina  is 
neutralized  with  sulphuric  acid  in  a  porcelain  evaporat- 
ing dish,  evaporated  to  dryness,  the  residue  treated 
with   a  little   sulphuric   acid,   evaporated   to   dryness 
again,  treated  with  water,  evaporated  to  dryness,  and 
ignited  at  low  red  heat,  cooled,  and  weighed. 

Wt.  sodium  sulphate  X  0.4366  =  wt.  of  sodium  oxide. 

445.  Total  sulphur.    Fuse  1  gram  in  a  large  crucible 
with  a  mixture  of  potassium  nitrate  and  potassium 
chlorate  for  about  half  an  hour.     Dissolve  the  fused 
mass  in  dilute  hydrochloric  acid  and  boil  the  solution 
with  strong  nitric  acid  for  half  an  hour,  filter  off  the 


ANALYSIS  OF  BLUE  PIGMENTS  AND  PAINTS.      209 

silica  and  precipitate  the  sulphuric  acid  with  barium 
chloride  in  the  usual  manner.  Filter,  ignite,  and  weigh 
as  barium  sulphate. 

From  the  weight  of  barium  sulphate  thus  obtained 
deduct  the  weight  found  in  446;  the  difference  is  the 
amount  due  to  sulphur  present  in  the  blue  as  sulphide. 

Wt.  barium  sulphate  X  0.1373  =  wt.  sulphur. 

446.  Combined  sulphuric  acid.  Dissolve  1  gram  in 
dilute  hydrochloric  acid.  Filter  off  the  silica,  make 
filtrate  alkaline  with  ammonia  and  then  just  distinctly 
acid  with  hydrochloric  acid,  and  treat  with  barium 
chloride  in  the  usual  manner.  The  precipitated  barium 
sulphate  is  filtered,  ignited,  and  weighed  as  usual. 

Wt.  barium  sulphate  X  0.3434  =  wt.  of  sulphur  tri- 
oxide. 

447.  ANALYSES  OF  ULTRAMARINES  BY  THE  AUTHOR. 

Ultra- 
marine 
Blue. 
I. 

Silica 39.26 

Alumina 25.60 

Sulphur -11.69 

Sulphur  trioxide    ..........  3 . 10 

Sodium  oxide 19 . 87 

Water 0.48 


100.00    100.00    100.00 


448.  ANALYSES  OF  ULTRAMARINES  BY  HURST. 

SnlnhatP             Soap  Calico  Paper 

Sulphate.  Makers.  Printers.  Makera. 

Silica 49.69  40.65  40.89  45.42 

Alumina 23.00  25.05  24.11  21.15 

Sulphur 9.23  12.95  13.74  11.62 

Sulphur  trioxide 2.46            4.81  3.05  5.58 

Soda ..-V.    .    .       12.49  14.26  15.61  9.91 

Water     . 3.13            2.28  2.60  6.32 

100.00  100.00  100.00  100.00 


210  PAINT  AND  VARNISH  PRODUCTS. 

Analysis  of  Cobalt  Blue. 

449.  This  pigment,  which  is  essentially  a  compound  of 
the  oxides  of  alumina  and  cobalt,  has  largely  gone  out  of 
use,  but  that.it  still  finds  a  limited  application  is  evi- 
denced by  the  fact  that  the  author  receives  occasionally 
samples  for  analysis.     Certain  shades  of  ultramarine 
blue  are  often  sold  under  the  name  of  cobalt  blue. 

450.  Moisture.     Determine  as  usual. 

451.  Alumina.    Fuse  1  gram  with  potassium  bisulphate 
as  described  under  analysis  of  Indian  reds  and  Venetian 
reds.     Dissolve  in  water  and  hydrochloric  acid,  filter, 
and  make  up  to  250  c.c.  in  a  graduated  flask.     Any 
residue  remaining  on  the  filter  paper  is  ignited  and 
weighed  as  silica,  unless  barium  sulphate  is  present, 
which  would  be  shown  by  the  flame  test. 

An  aliquot  portion  of  the  solution  is  treated  with  an 
excess  of  ammonium  chloride,  and  then  made  just  dis- 
tinctly alkaline  with  ammonia.  Filter,  dissolve  on  the 
filter  with  hydrochloric  acid,  and  reprecipitate.  Filter 
again,  combining  the  twt>  filtrates.  Wash  thoroughly, 
ignite,  and  weigh  as  alumina. 

452.  Calcium  and  magnesium.     The  combined  filtrates 
from  the  alumina  are  saturated  with  hydrogen  sulphide, 
filtered,  and  any  calcium  and  magnesium  estimated  in 
the  filtrate  in  the  usual  manner. 

453.  Cobalt  oxides.     The  oxides  of  cobalt  present  are 
best  estimated  by  difference,  by  subtracting  the  deter- 
mined constituents  from  100.     It  is  stated  by  Hurst 
that  phosphoric  acid  is  occasionally  used  in  the  manu- 
facture of  cobalt  blues,  in  which  case  it  should  be  re- 
moved before  estimating  the  aluminum,  calcium,  and 
magnesium.      The  several  samples  examined  by  the 
author  were  found  to  be  free  from  phosphoric  acid. 


CHAPTER  XXIV. 

ANALYSIS   OF  YELLOW,   ORANGE,  AND  RED   CHROME 
LEADS;  ANALYSIS   OF  VERMILIONS. 

454.  Composition.  The  lemon  yellow  chromes  usually 
contain  sulphate  of  lead,  sometimes  carbonate  of  lead. 
The  red  chromes,  known  by  the  various  names  of  scarlet 
chrome,  chrome  red,  Chinese  red,  American  vermilion, 
and  vermilion  substitute,  may  be  considered  as  basic 
chromates  of  lead.  Often  these  basic  chromes  are 
brightened,  up  by  having  precipitated  on  them  an 
organic  color;  this  may  be  tested  for  by  treating  a  por- 
tion of  the  pigment  with  alcohol,  which  will  dissolve  the 
organic  color,  giving  a  strongly  colored  solution.  See 
analysis  of  vermilions. 

455-  Hygroscopic  moisture.  Heat  2  grams  at  105°  C. 
for  3  hours.  Loss  in  weight  represents  hygroscopic 
moisture. 

456.  Barytes,  silica,  and  clay.     One  gram  of  the  pig- 
ment is  boiled  for  5  minutes  with  30  c.c.  of  concen- 
trated hydrochloric  acid  in  a  covered  beaker.     While 
boiling  add  half  a  dozen  drops  of  alcohol  one  at  a  time. 
Fifty  c.c.  of  water  is  added  and  the  boiling  continued 
for  10  or  15  minutes.     Filter,  wash  thoroughly  with 
boiling  water,  ignite,  and  weigh.     The  insoluble  resi- 
due is  fused  with  sodium  carbonate,  and  the  barium, 
silica,  and  alumina  separated  as  described  under  analysis 
of  white  paints. 

457.  Lead.    The  filtrate  from  the  insoluble  residue  is 
neutralized  with  dilute  ammonia  until  the  further  addi- 

211 


212  PAINT  AND  VARNISH  PRODUCTS. 

tion  of  another  drop  would  cause  the  formation  of  a  per- 
manent precipitate,  diluted  to  about  250  c.c.  to  300  c.c., 
and  hydrogen  sulphide  passed  in  for  10  minutes. 

Solutions  containing  large  amounts  of  chromium,  if 
neutralized  with  ammonia  until  a  permanent  precipi- 
tate appears,  seem  to  require  an  excess  of  hydrochloric 
acid  for  their  resolution,  sufficient  to  prevent  the  satis- 
factory precipitation  of  the  lead  with  the  hydrogen 
sulphide. 

Allow  the  precipitate  to  settle  thoroughly,  as  it  ren- 
ders the  filtering  much  easier,  filter,  wash  with  hydrogen 
sulphide  water.  Boil,  filter,  and  precipitate  with  dilute 
nitric  acid,  until  all  of  the  lead  has  dissolved,  filter  with 
aid  of  suction,  washing  thoroughly  with  hot  water. 
Add  5  c.c.  of  concentrated  sulphuric  acid,  diluted  with 
an  equal  volume  of  water,  to  the  filtrate.  Evaporate 
on  hot  plate  until  the  white  fumes  of  sulphur  trioxide 
appear.  Cool,  dilute  with  water,  add  an  equal  volume 
of  alcohol,  filter,  washing  with  dilute  alcohol,  ignite 
gently,  and  weigh  as  lead  sulphate.  Save  filtrate. 

458.  Chromium.  The  alcoholic  filtrate  from  the  lead 
sulphate  is  evaporated  nearly  to  dryness  to  expel  alco- 
hol, and  the  filtrate  from  the  lead  sulphide  heated  until 
the  hydrogen  sulphide  is  expelled.  The  two  filtrates 
are  mixed,  diluted  if  necessary,  and  made  just  percep- 
tibly alkaline  with  ammonia;  boil,  settle,  filter,  wash 
thoroughly,  ignite,  and  weigh  as  chromic  oxide. 

Wt.  chromic  oxide  X  1.3137  =  wt.  chromic  anhy- 
dride. 

Occasionally  these  pigments  contain  a  small  quan- 
tity of  iron,  which  should  be  tested  for  qualitatively 
in  a  separate  portion  of  the  pigment.  If  found  to  be 
present,  the  precipitate  of  ferric  and  chromium  hydrox- 
ides is  dissolved  on  the  filter  with  hydrochloric  acid, 


ANALYSIS  OF  CHROME  YELLOW,  ETC.  213 

the  filter  washed  thoroughly  with  hot  water,  and  the 
iron  and  chromium  in  the  filtrate  reprecipitated  with 
ammonia  and  treated  with  sodium  peroxide  to  dis- 
solve the  chromium  as  described  under  the  analysis 
of  chrome  greens. 

459.  Calcium.    The  filtrate  from  the   chromium  is 
treated  with  ammonium  oxalate,  allowed  to  stand  in  a 
warm  place  for  an  hour  or  so,  filtered,  washed  thor- 
oughly, strongly  ignited,  and  weighed  as  calcium  oxide. 

460.  Magnesium.     The  magnesium  is  estimated  in 
the  filtrate  from  the  calcium  in  the  usual  manner. 

461.  Combined  sulphuric  acid.   The  combined  sulphuric 
acid  may  be  estimated  by  either  of  the  two  methods 
given  in  the  chapter  devoted  to  the  analysis  of  white 
paints.    In  fact,  the  latter  method  may  be  used  for 
the  rapid  analysis  of  a  chrome  lead,  the  insoluble  lead 
carbonate  being  filtered  off,  the  chromium  precipitated 
as  the  hydroxide  in  the  usual  manner,  and  the  com- 
bined sulphuric  acid  estimated  in  the  filtrate  from  the 
chromium. 

Wt.  barium  sulphate  X  0.3433  =  combined  sulphu- 
ric acid. 

462.  Calculations.     If  calcium  is  absent,  or  present  as 
carbonate,  the  combined  sulphuric  acid  is  calculated  to 
lead  sulphate,  the  chromic  anhydride  to  lead  chromate, 
and  excess  of  lead  to  lead  oxide.     If  calcium  sulphate 
and  carbonate  of  lead  are  present,  the  carbon  dioxide 
must  be  determined  and  the  amount  of  calcium  present 
as  sulphate  estimated  by  Thompson's  method  as  de- 
scribed under  analysis  of  white  paints. 

Wt.  comb,  sulphuric  acid  X  3.788  =  wt.  lead  sul- 
phate. 

Wt.  chromic  anhydride  X  3.230  =  wt.  lead  chro- 
mate. 


214  PAINT  AND  VARNISH  PRODUCTS. 

Wt.  lead  chromate  X  0.6406  =  wt.  lead. 

Wt.  lead  X  1.0773  =  wt.  lead  oxide. 

The  specifications  for  chrome  leads  issued  by  the  U.  S. 
Treasury  Department,  1907,  state  that  a  color  contain- 
ing lead  sulphate  is  to  be  preferred  to  one  containing 
white  lead. 

463.   ANALYSES   OF  CHROME   LEADS   BY  AUTHOR. 

.      I    *£  H 

Moisture 0.04  0.03 

Lead  chromate 68.65  40.56 

Lead  oxide ' 47.24 

Lead  sulphate 31.21  5.49 

Silica 0.74 

Alumina ,    .         ...  0 . 44 

Organic  color ...  4 . 87 

Undetermined   .  0.10  0.63 


100.00         100.00 

Analysis  of  Mixed  Paints  Containing  Chrome  Yellows 
and  Ochres. 

464.  Barytes,  silica,  and  clay  are  estimated  as  described 
under  analysis  of  chrome  leads. 

465.  Lead,  both  as  sulphate  and  carbonate,  is  esti- 
mated as  described  under  chrome  leads,   the  filtrate 
from  the  lead  sulphate  being  saved  as  before. 

466.  Iron.    The  filtrate  from  the  lead  sulphide  is  heated 
until  all  of  the  hydrogen  sulphide  has  been  expelled  and 
added  to  the  filtrate  from  the  lead  sulphate  from  which 
the  alcohol  has  been  expelled  by  boiling.     A  few  drops 
of  nitric  acid  are  added  and  the  solution  boiled  for  a 
minute  or  two,  then  made  just  distinctly  alkaline  with 
ammonia,  boiled,  settled,  and  filtered. 

Dissolve  on  the  filter  with  hot  dilute  hydrochloric 
acid,  wash  with  hot  water.     Cool.     Reprecipitate  with 


ANALYSIS  OF  CHROME  YELLOW,  ETC.  215 

ammonia,  avoiding  excess,  without  waiting  for  the  pre- 
cipitate to  settle,  carefully  add  a  sufficient  quantity  of 
sodium  peroxide  (1  gram  is  usually  sufficient),  keeping 
the  beaker  covered  meanwhile.  Digest  until  all  of  the 
chromium  and  aluminum  have  passed  into  solution, 
adding  more  peroxide  if  necessary.  The  iron  remains 
undissolved,  while  the  chromium  and  aluminum  go  into 
solution;  filter,  wash  thoroughly,  ignite  strongly,  and 
weigh  as  ferric  oxide,  or  dissolve  in  dilute  hydrochloric 
acid  and  titrate.  The  treatment  with  peroxide  is  pref- 
erably performed  in  a  porcelain  evaporating  dish. 

467.  Chromium.     The  nitrate  from  the  iron  is  made  up 
to  250  c.c.  in  a  graduated  flask.     An  aliquot  portion  is 
rendered  acid  with  acetic  acid  and  a  slight  excess  of 
lead  nitrate  solution  added,  allowed  to  remain  on  the 
hot    plate    until   thoroughly   settled,    filtered   onto   a 
weighed  Gooch  crucible,  washed,  dried,  and  weighed  as 
lead  chromate. 

468.  Aluminum.     An  aliquot  portion  of  the  250  c.c. 
solution  is  made  just  acid  with  hydrochloric  acid,  and 
then  just  distinctly  alkaline  with  ammonia,  allowed  to 
settle,   filtered   onto   a  Gooch   crucible,   ignited,  and 
weighed  as  alumina. 

469.  Zinc.     The  filtrate  from  the  chromium,  iron  and 
aluminum  hydroxides,  under  iron  is  mixed  with  the  fil- 
trate from  the  lead  sulphate  from  which  the  alcohol 
has  been  expelled,  and  the  mixed  solution  saturated 
thoroughly  with  hydrogen  sulphide,  boiled  with  the 
addition  of  solid  ammonium  chloride  to  render  the  pre- 
cipitate less   slimy,  and   filtered.     The   zinc   sulphide 
dissolved  with  hydrochloric  acid,  boiled  to  expel  hydro- 
gen sulphide,  and  titrated  with  standard  ferrocyanide 
of   potassium   as   described   under   analysis    of  white 
paints. 


216  PAINT  AND  VARNISH  PRODUCTS. 

470.  Calcium,  magnesium,  and  combined  sulphuric  acid 
are  estimated  as  described  under  analysis  of   chrome 
leads  and  the  calculations  made  as  there  described. 

Analysis  of  Vermilion. 

471.  Properties.     Vermilion  is  a  bluish  scarlet  powder, 
having  a  specific  gravity  of  8.2.     It  is  insoluble  in  any 
single  acid  such  as  hydrochloric  or  nitric  acid  and  in 
the  alkalies.     Heated  in  contact  with  the  air,  it  burns 
with  a  pale  blue  lambent  flame.     Pure  vermilion  will 
burn  away  entirely  or  at  least  leave  but  a  small  fraction 
of  1  per  cent  of  ash.     This  is  a  reliable  test  for  it,  as 
other  adulterants  would  be  left  behind  on  heating. 

The  most  common  adulterants  of  vermilion  are  red 
lead,  oxide  of  iron,  lead  chromes,  vermilionette  lakes, 
para  reds,  and  alizarine  reds. 

472.  Detection    of    vermilionettes,    para    and    alizarine 
reds,     (a) .  Boil  a  little  of  the  dry  color  with  water,  set- 
tle, and  filter.     Vermilionettes  give  a  deep  red  solution, 
para  reds  a  pale  brownish  or  orange,  and  the  alizarine 
reds  a  colorless  solution. 

(6).  Boil  a  little  of  the  dry  color  with  a  mixture  of 
methyl  and  ethyl  alcohol,  filter,  heat,  and  settle.  Ver- 
milionettes give  a  bright  red  solution,  usually  having 
a  yellow  "bloom,"  para  reds  an  orange-red  solution, 
alizarine  reds  a  practically  colorless  solution. 

(c).  Boil  another  portion  of  the  dry  pigment  with 
some  freshly  distilled  aniline,  settle,  and  filter.  Ver- 
milionettes give  a  purple-red,  alizarine  lakes  a  pale 
brown,  and  the  para  reds  an  intense  orange-red  solu- 
tion. 

(d).  Boil  some  of  the  dry  color  with  a  solution  of 
caustic  soda.  Vermilionettes  give  a  red  solution  with 


ANALYSIS  OF   CHROME  YELLOW,   ETC.  217 

a  green  "bloom,"  para  reds  a  bluish  red  solution, 
while  alizarine  reds  yield  a  characteristic  deep  violet 
solution. 

473.  Barytes,  silica,  and  clay.     Dissolve  1  gram  in  30 
c.c.  of  concentrated  hydrochloric  acid,  50  c.c.  of  water 
with  the  aid  of  1  to  2  grams  of  potassium  chlorate  added 
in  small  portions  and  warming.     Evaporate  to  dryness 
on  water  bath.     Take  up  in  50  c.c.  of  water  acidulated 
with  hydrochloric  acid,  heat  to  boiling  to  dissolve  any 
lead  chloride,  filter,  wash  with  boiling  water,  ignite,  and 
weigh  any  insoluble  residue.     Fuse  with  sodium  carbon- 
ate and  estimate  the  barium  sulphate,  silica,  and  alu- 
mina as  described  under  analysis  of  white  paints. 

474.  Lead.     If  lead  is  present,   calcium  compounds 
being  absent,  the  filtrate  is  treated  with  sulphuric  acid, 
evaporated  carefully  to  expel  excess  of  hydrochloric 
acid,  diluted  with  water  and   alcohol,  the  lead  sul- 
phate filtered  off  on  a  Gooch  crucible  in  the  usual 
manner. 

475.  Mercuric  sulphide  (vermilion).     The  filtrate  from 
the  insoluble  residue,  if  lead  is  absent,  or  the  filtrate 
from  the  lead  sulphate,  is  heated  with  a  little  sulphur- 
ous acid  to  reduce  any  iron  present  to  the  ferrous  con- 
dition, made  neutral  with  ammonia,  and  then  just  acid 
to  litmus  with  hydrochloric  acid. 

The  solution  is  diluted  to  about  350  c.c.  and  hydro- 
gen sulphide  passed  in  for  10  minutes.  The  mercuric  sul- 
phide is  filtered  off  on  a  weighed  Gooch  crucible,  washed 
with  hydrogen  sulphide  water,  the  crucible  removed  to 
another  holder  and  washed  with  alcohol  and  carbon 
bisulphide  to  remove  sulphur,  dried  in  steam  oven,  and 
weighed. 

476.  Estimation   of   lead   and   mercury,    calcium   com- 
pounds present.    The  filtrate  from  the  insoluble  residue 


218 


PAINT  AND  VARNISH  PRODUCTS. 


from  473  is  precipitated  with  hydrogen  sulphide  as  de- 
scribed under  475,  collected  on  a  weighed  filter,  and 
dried  at  100°  C.,  weighed,  and  mixed  uniformly. 

An  aliquot  part  is  introduced  into  the  bulb  of  Fig.  10, 
a  slow  stream  of  washed  chlorine  gas  passed  through  it, 


FIG.  10. 

and  a  gentle  heat  applied  to  the  bulb,  increasing  this 
gradually  to  faint  redness.  The  escaping  chlorine  is 
conducted  into  a  flue.  First,  sulphur  chloride  distills 
over,  which  decomposes  with  the  water  in  E  and  F. 
The  mercuric  chloride  formed  volatilizes,  condensing 
partly  in  E,  partly  in  0.  Cut  off  that  part  of  the  tube, 
rinse  the  mercuric  chloride  into  E,  and  mix  the  contents 
of  the  latter  with  the  water  in  F.  Mix  the  solution 
with  excess  of  ammonia  and  warm  gently  until  no  more 
nitrogen  is  evolved,  acidify  with  hydrochloric  acid,  fil- 
ter, and  determine  the  mercury  in  the  filtrate  as  under 
475. 

477.  Ferric  oxide.  The  filtrate  from  the  sulphides  is 
heated  until  all  of  the  hydrogen  sulphide  has  been  ex- 
pelled and  the  iron  chromium  and  alumina  precipitated 
with  ammonia,  filtered  and  separated  as  described  under 
analysis  of  chrome  greens. 


ANALYSIS   OF  CHROME  YELLOW,   ETC.  219 

478.  Zinc  oxide.     The  filtrate  from  the  iron  and  alu- 
mina precipitate  is  made  distinctly  alkaline  with  am- 
monia and  the  zinc  precipitated  with  hydrogen  sulphide. 
The  liquid  containing  the  zinc  sulphide  precipitate  is 
heated  to  boiling,  and  about  5  grams  of  solid  ammonium 
chloride  added,  which  renders  the  precipitate  easier 
to  filter.     Settle,  filter,  wash  thoroughly.     Pierce  filter, 
wash  through  into  a  clean  beaker  with  water,  dissolv- 
ing the  residue  on  filter  with  dilute  hydrochloric  acid, 
and  washing  with  hot  water.     Dilute,  heat  to  expel 
hydrogen  sulphide,  and  titrate  with  ferrocyanide  as  pre- 
viously described.     If  iron  is  absent  in  the  paint,  the 
zinc  may  be   estimated   directly  as   described  under 
analysis  of  white  pigments. 

479.  Calcium  and  magnesium.     Estimated  as  usual  in 
the  filtrate  from  the  zinc  sulphide. 

480.  Calculations.     If  chromium  is  present  it  is  cal- 
culated to  basic  lead  chromate,  and  any  excess  of  lead 
above  that  required  to  form  the  chromate  is  calculated 
to  red  lead. 

481.  ANALYSES  OF  VERMILIONS  BY  THE  AUTHOR. 

I.       II.     ill. 

English  English 

Vermilion.        Vermilion.      Vermilion. 
Deep.  Pale. 

Sulphide  of  mercury     ....       99.53          99.61  99.61 

Ash  0.47  0.39  0.39 


100.00    100.00  100.00 

I.  II. 

,  Radium 

Vermilion.  ,..        ... 

Vermilion. 

Moisture 0.16  0.06 

Red  lead 80.08  97.99 

Barytes 16.83 

Alumina 0 . 77 

Organic  color 2.16  1.95 

100.00  100.00 


220 


PAINT  AND  VARNISH  PRODUCTS. 


Moisture 

I. 

Light 
Vermilion. 

1  33 

II. 

Deep 
Vermilion. 

0  15 

Lead  chromate 

50  16 

53  60 

Lead  oxide 

41  20 

40  88 

Lead  sulphate 

6  15 

4  97 

Ferric  oxide  •        

0  37 

0  33 

Soluble  salts      

...                    0  33 

trace 

Undetermined   

0  46 

0  07 

100.00         100.00 

482.  Antimony  vermilion  and  orange.  These  two  pig- 
ments have  the  same  composition,  corresponding  to  the 
formula  of  antimony  trisulphide.  They  are  insoluble 
in  dilute  acids,  but  soluble  in  strong  hydrochloric  acid. 
It  is  seldom  necessary  to  make  a  complete  analysis  of 
these  pigments.  Adulteration  will  be  indicated  by  the 
pigment  not  being  completely  soluble  in  strong  hydro- 
chloric, though  a  trace  of  sulphur  may  remain  undis- 
solved,  floating  on  top  of  the  acid. 


CHAPTER  XXV. 

ANALYSIS  OF  RED  LEAD,   ORANGE  MINERAL,  AND 
LITHARGE. 

483.  Red  lead.     This  pigment,  corresponding  to  the 
formula  Pb304,  is  prepared  by  three  different  processes : 

1.  The  dressing  process,  in  which  a  puddle  of  molten 
lead  is  slowly  drossed  in  a  reverberatory  furnace  by  con- 
stant rabbling,  and  the  dross  or  massicot  thus  obtained 
is  water  ground  and  floated  to  free  from  metal  particles 
and  calcined  for  about  48  hours  at  a  definite  tempera- 
ture in  another  reverberatory  furnace.     The  product  is 
usually  bolted  through  a  silk  bolting  cloth. 

2.  The  nitrate  process,  in  which  metallic  lead  and 
nitrate  of  soda  are  fused  together,  yielding  an  oxide  of 
lead  (PbO)  and  nitrite  of  soda  (NaN02).     This  oxide, 
after  having  been  thoroughly  leached  to  remove  the 
nitrite,  is  calcined  and  finished  as  above  described. 
The  nitrite  of  soda  obtained  by  this  process  has  a 
large  use  in  the  manufacture  of  para  reds.     Red  lead 
manufactured  by  this  process  will  usually  contain  a 
small  amount  of  caustic  soda  and  nitrite  of  soda. 

3.  The  basic  oxide  process,  in  which  molten  lead  is 
Very  finely   subdivided   by  superheated   steam,    con- 
verted into  a  basic  oxide  by  agitation  with  air  and 
water,  dried,  ground,  and  calcined  for  about  15  hours, 
which  is  sufficient  to  develop  the  full  color.     This  proc- 
ess represents  the  latest  and  most  advanced  stage  of 
oxide  manufacture,  yielding  for  many  purposes  a  much 
superior  product. 

221 


222  PAINT  AND  VARNISH  PRODUCTS. 

484.  A  thorough  physical  examination  of  red  lead  is 
of  fully  as  much  importance  as  a  chemical  analysis. 

485.  Microscopical    examination.      Under   the   micro- 
scope the  red  lead  should  show  freedom  from  metallic 
particles,  vitrified  red-lead  particles,  and  foreign  matter 
such  as  coal  dust,  furnace  grit,  etc. 

486.  Fineness.      Less  than  one-tenth  of  1  per  cent 
should  be  retained  on  a  screen  composed  of  number  20 
or  21  silk  bolting  cloth. 

487.  Color.     The  color  of  red  lead,  as  of  the  chrome 
leads,  depends  on  the  size  of  the  particles:  the  larger 
the  particles  the  deeper  the  tone,  and  the  smaller  the 
particles  the  paler  the  color  but  with  a  marked  in- 
crease of  fire  and  brilliancy.     For  the  manufacture  of 
reduced  red  leads  and  of  vermilions  the  deep  tones  are 
the  most  desirable,  as  they  require  less  dye. 

488.  Bulking   figure.      Hitherto,  the  great   objection 
to  the  use  of  red  lead  for  painting  structural]  iron  and 
steel  work  has  been  its  excessive  tendency  to  settle  in 
the  paint  pot,  preventing  uniform  application  and  a 
manifest  sagging  and  streaking.     This  is  due  both  to 
the  density  and  the  comparative  large  size  of  the  red- 
lead  particles  as  compared  with  other  well-known  pig- 
ments.    The  first  two  processes  above  described  produce 
a  red  lead  having  these  characteristics,  while  the  third 
affords  a  very  soft,  bulky,  amorphous  red  lead,  the 
particles  of  which  are  of  a  very  uniform  fineness.     In 
fact,  red  lead  made  by  this  process  much  resembles 
orange  mineral,  having  considerable  fire  and  brilliancy, 
and  does  not  readily  settle  in  the  paint  pot  or  sag  on 
vertical  surfaces. 

Other  factors  being  equal,  the  bulkiest  or  least  dense 
red  lead  is  the  most  desirable  for  painting  purposes. 
Red  leads  made  by  the  first  two  processes  give  a  bulking 


ANALYSIS  OF  RED  LEAD,  ORANGE   MINERAL,  ETC.     223 

figure  of  from  23  grams  to  32  grams  per  cubic  inch  by 
the  Scott  volumeter. 

489.  If   a  liberal  percentage  of  carbonate   tailings 
from  the  Dutch  process  of  white-lead  manufacture  has 
been  used,  the  bulking  figure  may  go  as  low  as  20  grams. 
The  third  process  yields  a  red  lead  having  a  bulking 
figure  of  15  grams  to  18  grams.     The  writer  firmly  be- 
lieves that  users  of  red  lead  would  secure  a  much  in- 
creased service  value  if  they  would  specify  a  red  lead 
having  a  bulking  figure  of  20  grams  or  under. 

490.  Painting  test.     When  mixed  with  pure  linseed 
oil,  pure  turpentine  and  Japan  drier  as  per  the  U.  S. 
Navy  Department  formula  (1909),  viz: 

Red  lead,  dry 17  pounds 

Raw  linseed  oil      4|  pints 

Spirits  of  turpentine 1  gill 

Japan  drier 1  gill 

and  applied  to  a  smooth,  vertical  iron  surface,  it  must 
dry  solidly  without  running,  streaking,  or  sagging.  It 
should  be  noted  that  while  this  formula  affords  a  good 
test  for  red  leads  of  a  moderate  bulking  figure,  it 
affords  a  mix  entirely  too  thick  with  a  red  lead  having 
a  bulking  figure  of  15  grams  to  18  grams. 

491.  Free  Litharge.    The  free  litharge  content  of  red 
lead  is  a  rather  variable  quantity;  it  may  go  as  high  as 
25  per  cent  or  as  low  as  1  per  cent,  the  average  being 
perhaps  between  6  and  12  per  cent.     No  absolutely  sat- 
isfactory method  has  yet  been  devised  for  its  determina- 
tion.    The  acetate  method  is  probably  as  satisfactory 
as  any. 

492.  Weigh  10  grams  of  the  sample  into  a  150  c.c. 
beaker  provided  with  a  cover  glass,  add  25  c.c.  of  a 
neutral  normal  solution  of  acetate  of  lead  and  50  c.c. 
of  freshly  boiled  distilled  water.     Boil  gently  for  ex- 


224  PAINT  AND  VARNISH  PRODUCTS. 

actly  5  minutes.  Decant  onto  a  Gooch  crucible,  wash 
by  decantation  with  boiling  water  twice,  collect  residue 
on  crucible,  and  wash  thoroughly  with  boiling  water, 
then  with  a  few  drops  of  alcohol  dry  in  steam  oven, 
cool,  and  weigh.  The  weight  of  the  residue  subtracted 
from  10  indicates  the  amount  of  free  litharge  present. 
The  government  specifications  require  at  least  94  per 
cent  true  red-lead  content,  which  insures  a  litharge  con- 
tent of  6  per  cent  or  less. 

493.  Peroxide  content.  Numerous  methods  have  been 
devised  for  determining  the  peroxide  content  of  red 
lead.  Mannhardt's  method  is  perhaps  the  most  accu- 
rate. 

Weigh  out  1  gram  of  the  pigment.  Triturate  this 
with  1.176  grams  of  ammonium  ferrous  sulphate  crys- 
tals. 0.1176  gram  of  the  salt  corresponds  to  1  c.c.  of 
3  N-10  (oxidizing)  solution  and  to  .03585  Pb02.  The 
trituration  is  carried  out  carefully.  The  mixture  is 
then  brushed  into  a  small  beaker  and  about  10  grams 
commercial  ammonium  chloride  added.  This  is  mois- 
tened and  the  pigment  stirred  in  and  20  c.c.  of  water 
and  20  c.c.  of  hydrochloric  acid  added.  The  mixture 
is  warmed  on  the  steam  plate  and  then  titrated  for 
excess  of  ferrous  iron  with  a  3  N-10  oxidizing  solution  of 
bichromate  (29.5  grams  to  2  liters),  using  a  pale  yellow 
solution  of  potassium  ferrocyanide  as  external  indicator. 
The  ferrous  solution  must  be  very  strongly  acid  when 
nearing  the  endpoint,  in  order  to  obtain  a  very  definite 
endpoint. 

The  weight  of  ferrous  ammonium  sulphate  used  in 
the  determination  of  the  peroxide  should  be  about 
5  per  cent  in  excess  of  the  theoretical  consumption. 

The  range  of  consumption  of  ferrous  salt  will  vary 
between  7  c.c.  and  9.6  c.c.  of  the  bichromate  solution. 


ANALYSIS  OF  RED  LEAD,  ORANGE   MINERAL,  ETC.     225 

494.  Orange  mineral.     This  product  may  be  consid- 
ered as  a  debased  form  of  red  lead,  inasmuch  as  it  is 
not  so  stable  toward  light  as  red  lead.     It  is  usually 
prepared  by  calcining  white-lead  residues  or  tailings. 
Its  specific  gravity  is  much  lower  than  that  of  red  lead. 
It  may  be  differentiated  from  red  lead  by  microscopical 
examination.     Under  a  magnification   of  400  to  500 
diameters  the  particles  of  red  lead  much  resemble  small 
crystals  of  bichromate,    being  distinctly  transparent, 
while  orange-mineral  particles  are  much  smaller  and 
quite  opaque. 

495.  The  same  physical  and  chemical  determinations 
that  apply  to  red  lead  apply  to  orange  mineral.     The 
litharge  content  of  orange  mineral  is  usually  very  low, 
and  for  this  reason  it  is  often  ground  in  linseed  oil  and 
put  on  the  market  in  paste  form,  whereas  the  higher 
litharge  content  of  red  lead  would  cause  "livering" 
and  hardening  in  the  package  except  in  occasional  in- 
stances when  a  very  carefully  selected  red  lead  is  used. 

496.  Litharge.    The  different  brands  of  litharge  found 
on  the  market  will  vary  greatly  in  color  and  other  physi- 
cal characteristics,  which  are  determined  by  the  prefer- 
ence of  the  buyer.     The  three  leading  impurities  which 
are  of  interest  to  the  paint  chemist  are  metallic  lead,  sul- 
phates, and  red  lead,  all  three  usually  being  classed  to- 
gether as ' '  insoluble  matter. ' '     The  metallic  lead  and  red 
lead  are  particularly  objectionable  to  the  color  maker, 
as  they  affect  the  purity  of  the  tint  of  his  colors,  they 
not  being  soluble  in  acetic  acid.     The  insoluble  matter 
may  be  determined  by  boiling  5  grams  of  the  sample 
with  dilute  acetic  acid,  filtering  onto  a  Gooch  crucible, 
washing  thoroughly  with  hot  water,  drying,  and  weigh- 
ing.    The  insoluble  matter  should  not  exceed  0.6  per 
cent. 


226  PAINT  AND  VARNISH  PRODUCTS. 

497.  Carbon   dioxide.     Freshly   prepared   litharge   is 
free  from  combined  carbon  dioxide,  as  the  temperature 
at  which  it  is  furnaced  is  more  than  sufficient  to  de- 
compose any  carbonate  of  lead  that  might  be  present. 
On  exposure  to  air,  however,  litharge  absorbs  carbon 
dioxide  in  notable  quantities.     This  is  especially  true  of 
samples  of  litharge  sent  by  mail  in  paper  envelopes  or 
of  samples  allowed  to  remain  in  the  laboratory.     The 
determination  of  carbon  dioxide  can  be  made  in  the 
usual  manner,  although  the  shipment  of  goods  in  bulk 
will  usually  show  practically  entire  absence  of  carbon 
dioxide. 

498.  Sulphates.     The  commercial  grades  of   litharge 
will  contain  a  small  fraction  of  1  per  cent  of  sulphate  of 
lead,  due  to  the  sulphur  gases  from  the  coal  used  in  the 
furnacing.     The  sulphate  content  can  be  determined 
as  stated  in  the  chapter  devoted  to  the  analysis  of 
white  lead.     The  small  quantity  usually  found  is  not 
objectionable  for  dry-color  manufacture,  as  it  under- 
goes conversion  with  the  chromates  used  and  therefore 
may  be  deducted  from  the  total  insoluble  matter,  thus 
affording  the  percentage  of  distinctly  objectionable  im- 
purities, viz.,  metallic  lead  and  red  lead. 


CHAPTER  XXVI. 

ANALYSIS  OF  PAINTS  FOR  MANUFACTURING  PURPOSES. 

499.  Classification.     Under  the  above  heading  is  in- 
cluded an  immense  variety  of  paint  products,  the  ma- 
jority of  which  are  sold  in  paste  or  semi-paste  form,  the 
thinning  down  being  accomplished  by  the  purchaser. 
The  most  common  use  is  for  agricultural  machinery, 
such  as  harvesters,  threshers,  wagons,  plows,  etc.,  the 
paint  usually  being  applied  by  the  " dipping"  process. 
A  large  amount  of  paints  is  used  for  bedsteads,  refrig- 
erators, etc.     Considerable  amounts  of  paint  are  used 
in  the  manufacture  of  toys,  as  primers  for  sashes  and 
doors,  for  shade  cloth,  oilcloth,  trunks,  etc.     Bridge 
paints,  structural  iron  and  steel  paints,  and  paints  for 
the  railroad  trade  also  form  a  very  important  class  of 
paint  products. 

500.  Analysis.    The  analysis  of  these  various  paint 
products  offers  no  particular  difficulties,  and  the  schemes 
outlined  in  other  chapters  for  the  various  colors  will  be 
found  to  be  satisfactory  in  the  majority  of  instances. 
Immense  quantities  of  para  reds,  precipitated  on  vari- 
ous inert  bases  such  as  barytes,  china  clay,  magne- 
'sium  silicate,  etc.,  are  used  in  agricultural  paints.     The 
actual  amount  of  para  red  used  is  the  most  important 
factor  in  determining  the  cost  or  selling  price  of  such 
paints.     The  amount  present  can  be  determined  ap- 
proximately by  difference,   i.e.,   by   determining  the 
combined  percentage  of  inert  materials  and  subtracting 
from  100.     Unless  the  determinations  are  performed 

227 


228  PAINT  AND  VARNISH  PRODUCTS. 

with  extreme  care  and  discrimination,  serious  errors 
are  liable  to  be  made,  and  it  is  often  advisable  to  check 
the  analysis  by  a  determination  of  the  amount  of  para 
red  present,  which  can  be  accomplished  by  determining 
the  percentage  of  nitrogen  by  the  Kjeldahl  method, 
modified  as  for  nitrates,  as  the  diazo  radical  is  so  easily 
broken  down  that  unless  considerable  care  is  observed 
a  loss  of  nitrogen  compounds  will  occur.  The  Kjeldahl 
method  is  given  in  full  in  the  various  published  reports 
of  the  Association  of  Official  Agricultural  Chemists. 

501.  Presence  of  color  lakes.     If  the  color  of  the  paint 
varies  materially  from  that  obtained  with  a  straight 
para  red,  other  organic  colors,  as  eosine,  Bordeaux  B, 
Scarlet  No.  1,  etc.,,  may  be  present,  in  which  case  the 
nitrogen  determination  is  to  a  large  extent  valueless. 
For  the  detection  of  the  different  organic  colors  present 
the  author  has  found  the  "  Treatise  on  Color  Manu- 
facture," by  Zerr,  Rubencamp  and  Mayer,  the  most 
thorough  and  comprehensive  of  any  yet  published. 

It  should  be  remembered  that  while  the  principles 
underlying  the  manufacture  of  the  para  reds,  so  called, 
are  well  known,  yet  certain  color  makers  are  enabled 
to  produce  more  brilliant  and  stronger  reds  than  others; 
and  in  attempting  to  duplicate  a  manufacturing  trade's 
paint  containing  a  para  red  the  question  of  inherent 
strength  and  brilliancy  must  be  taken  into  considera- 
tion. 

502.  Analyses.     The  following  analyses  made  in  the 
author's  laboratory  show  some  of  the  combinations  in 
use  by  the  leading  manufacturers  of  agricultural  ma- 
chinery implements,  shade  cloth,  beds,  etc. 


PAINTS  FOR  MANUFACTURING  PURPOSES.          229 


VERMILION  PRIMERS. 

I.  II.                 III. 

w  Seeding  Ma-      Harvester 

T>  ,. «  TT*  chinery.          Machinery. 

!ent<  Per  cent.          Per  cent. 

White  lead     .    .    . 25.24 

Zinc-lead  white 27.86 

Lithopone '. ...             60 . 62 

Barium  sulphate 5 . 80  15 . 18 

Barium  carbonate ...  52 . 74 

Calcium  carbonate 66.97  ...             36.80 

Iron  oxide ...  ...               1 . 25 

Para  red.                                                  1.99  4.22            1.33 


100.00  100.00        100.00 

PRIMING  ENAMEL  — BEDS. 

I.  II. 

Per  cent.  Per  cent. 

Lithopone 49.04  63.37 

Zinc  oxide 2.60  22.50 

Calcium  carbonate 48.27  13.85 

99.91  99.72 

WHITE  BARREL  PASTE. 

Per  cent. 

Zinc  oxide 39.85 

Calcium  carbonate 60 . 15 


100.00 
SHADE  CLOTH,   BODY  WHITE. 

Per  cent. 

Lithopone 33.21 

Silica 1.98 

Calcium  carbonate 64 . 51 

99.70 

-*  •• 

YELLOW  AND  GREEN  PASTES  —  PLOWS,  WAGONS,  PUMPS, 
PLANTING  MACHINERY,   ETC. 

I.  n. 

Wagon  Primer.  Wagon  Finish- 

Percent-  PeV^ent 

Leadchromate 10.75  34.00 

Calcium  carbonate 47.60  66.00 

Barium  sulphate 41 . 65 

100.00  100.00 


230 


PAINT  AND  VARNISH  PRODUCTS. 


YELLOW  AND  GREEN  PASTES  — PLOWS,  WAGONS,  PUMPS, 
PLANTING  MACHINERY,  ETC.  —  Continued. 


Lead  chromate  .  . 
White  lead.  .  .  . 
Zinc  oxide  .... 
Calcium  carbonate 


I. 

Yellow 

Wagon 

Paste. 

Per  cent. 

8.32 

65.70 
13.20 
12.78 

100.00 


II. 

Yellow 

Pump 

Paste. 

Per  cent. 

50.22 


49.78 
100.00 


III. 

Yellow 

Wagon 

Paste. 

Per  cent. 

12.09 


58.35 
29.39 

99.83 


CREAM   PASTE  — HARVESTER. 


Lithppone  .... 
Calcium  carbonate 

Ochre 

Chrome  yellow  .    . 


Per  cent. 

48.64 

48.79 

1.08 

1.49 

100.00 


Chrome  green  .  . 
Zinc  oxide  .... 
Barium  sulphate  . 
Calcium  carbonate 
Aluminum  silicate 


I. 

Green 

Paste  — 

Farm 

Machinery. 

Per  cent. 

2.83 
36.89 

8.67 
51.61 


II. 

Green 
Paste  — 

Wagon. 
Per  cent. 

20.01 

39  .'85 


100.00 


100.00 


I. 

Green  Plow 

Paste. 
Per  cent. 

Chrome  green 5 . 00 

Zinc  lead 58.51 

Barium  sulphate 13 . 70 

Calcium  carbonate   .  22 . 79 


100.00 


II. 

Green  Plow 

Paste. 
Per  cent. 

4.92 


10.57 
84.51 


100.00 


PAINTS  FOR  MANUFACTURING  PURPOSES. 


231 


RED  WAGON  PASTES. 

I. 

Per  cent. 

Zinc  oxide 12.05 

Barium  sulphate 42 . 00 

Calcium  carbonate 30 . 09 

Aluminum  silicate ... 

Red  lead     .    .    .    . 

Para  lake 15.86 


100.00 


II. 

Per  cent. 


87.52 
2.45 

l6!  03 
100.00 


III. 

Per  cent. 

7.35 
37.80 


44.44 
10.41 

100.00 


IV. 

Per  cent. 

Barium  sulphate 50 . 25 

Red  lead 41.26 

Calcium  carbonate ... 

Para  lake    .    .    .  8.491 


100.00 
1  Includes  eosine. 


v. 

Per  cent. 


43.65 
51.38 
4.971 

100.00 


VI. 

Per  cent. 
9.52 

62.78 

23.66 

4.04 

100.00 


RED  LADDER  PASTE. 

Per  cent. 

Barium  sulphate 72.37 

Red  lead 20.28 

Para  lake 7.35 

100.00 
RED  PLOW  PASTE. 

Per  cent. 

Zinc  oxide 11.15 

Barium  sulphate 44 . 35 

Calcium  carbonate 30 . 68 

Para  lake 13.82 

100.00 
RED  THRESHER  PASTE. 

Per  cent. 

Zinc  oxide 9 . 95 

Barium  sulphate 53 . 45 

Calcium  carbonate .  20.20 

Para  lake 16.40 


100.00 


232  PAINT  AND  VARNISH  PRODUCTS. 


RED  SEEDING  MACHINERY  PASTE. 

Per  cent. 

Barium  sulphate .       17.10 

Calcium  carbonate 63 . 58 

Red  lead 12.80 

Para  lake 6.52 


100.00 

503.  Dipping  paints.  As  previously  stated,  a  large 
portion  of  the  agricultural  machinery  and  implement 
paints  is  applied  by  what  is  known  as  the  dipping  proc- 
ess, i.e.,  the  articles  to  be  painted  are  dipped  in  large 
tanks  of  the  thinned  paint.  It  is  obviously  necessary 
that  the  pigments  used  should  be  carefully  and  thor- 
oughly ground  and  of  as  non-settling  a  nature  as  pos- 
sible. These  features  are  of  as  much  importance  as 
the  chemical  composition. 


CHAPTER  XXVII. 

COMPOSITION  AND  ANALYSIS  OF  FILLERS. 

504.  Under  the  heading  of  fillers  are  included  paste 
and  liquid  wood  fillers,   crack  and  crevice  fillers,  iron 
fillers,  and  rough  stuff.     The  composition  and  proper- 
ties of  these  various  fillers  will  be  considered  separately. 

505.  Wood  fillers.     The  fact  that  many  of  the  wood 
fillers  on  the  market  are  of  inferior  quality  is  not  due 
to  lack  of  knowledge  of  the  manufacturer  but  to  the 
question  of  price.     The  pigment  portion  of  a  high-grade 
paste  wood  filler  should  consist  of  70  to  80  per  cent  of  a 
finely  ground  quartz,  such  as  Bridgeport  silica,  which 
possesses  a  decided  "  tooth."     The  remaining  portion, 
30  to  20  per  cent,  may  be  a  " toothless"  silicate  like  the 
well-known  F.  S.  A.  silica.     The  addition  of  1  to  2  per 
cent  of  powdered  starch  is  also  of  material  benefit. 
The  vehicle  should  be  composed  of  a  good  medium- 
drying  oil  Japan,  raw  linseed  oil,  and  turpentine;  water 
should  be  absent. 

The  cheapening  of  wood  fillers  is  accomplished  by 
using  an  inferior  benzine-rosin  Japan  and  a  cheap  white 
silicate  in  place  of  the  crushed  quartz  silica,  the  former 
'  being  obtained  at  about  one-third  of  the  cost  of  the 
latter.  Sometimes  white  mineral  primer  may  be  added 
for  cheapening.  Besides  the  customary  chemical  an- 
alysis, a  careful  microscopic  examination  should  be 
made  in  order  to  differentiate  the  silicas  used,  the 
crushed  quartz  silica  being  recognized  by  the  charac- 
teristic wedge-shaped  structure  of  the  particles;  the 

233 


234  PAINT  AND  VARNISH  PRODUCTS. 

fineness  of  the  particles  being  regulated  according  to  the 
nature  of  the  wood  to  be  filled,  open-grained  woods  re- 
quiring a  filler  containing  quite  a  percentage  of  com- 
paratively coarse  particles. 

506.  Tinted  wood  fillers  contain  small  percentages 
of  tinting  colors  such  as  ochre,  bone  black,  burnt  umber, 
Vandyke  brown;  golden  oak  being  obtained  with  the 
aid  of  ochre,  burnt  umber,  and  Vandyke  brown;  light 
oak  with  the  use  of  a  little  ochre  only;  dark  and  light 
antique  with  the  aid  of  burnt  umber;  and  walnut  with 
the  aid  of  an  asphaltum  black. 

507.  Transparent  liquid  wood  fillers  or  surfacers  for 
hard,  close-grained  woods  usually  contain  only  16  to 
20  per  cent   of  pigment,  which  may  be  white   filler 
(talcum),  or  better,  a  mixture  of  crushed  quartz  silex 
and  white  filler.     The  vehicle  should  be  a  light,  quick, 
hard-drying   kauri    varnish  with    turpentine    thinner. 
Kerosene-oil-and-water  emulsions  have  no   legitimate 
place  in  this  class  of  goods,  although  often  present. 
Instead  of  kauri  varnish,  a  rosin-china  wood-oil  var- 
nish is  often  used,  but  is  apt  to  cause  considerable 
trouble,  as  on  sandpapering  it  will  either  dust  or  soften 
and  roll  up  under  the  paper. 

508.  Crack  and  crevice  fillers.     The  basis  of  this  class 
of  goods  is  usually  powdered  starch,  raw  linseed  oil, 
benzine  Japan,  and  naphtha,  which  affords  a  cheap, 
efficient  paste  for  the  purpose  indicated. 

The  following  formula  is   typical  of  this  class  of 
products : 

Starch 100  Ibs. 

Raw  linseed  oil 3f  gal. 

Benzine  drier      H  gal. 

Benzine 1|  gal. 

509.  Iron  fillers.     This  class  of  paints  is  always  sold 
in  paste  form  and  may  contain  a  small  percentage  of 


COMPOSITION  AND  ANALYSIS  OF  FILLERS.          235 

white  lead  or  zinc  lead,  Keystone  filler,  white  filler, 
silica,  barytes,  or  white  mineral  primer  ground  in  lin- 
seed oil  and  Japan.  The  low  price  at  which  these 
fillers  are  sold,  3  to  4  cents  per  pound,  precludes  the 
use  of  any  large  percentage  of  lead  pigments. 

510.  Analyses.     The  following  analyses  indicate  the 
nature  of  some  of  the  iron  fillers  on  the  market : 

i.  n.  m. 

White.  Black.  Maroon. 

Per  cent.  Per  cent.  Per  cent. 

Barium  sulphate 40.85  ...               37.40 

White  lead 16.12  5.26 

Calcium  carbonate 43 . 03 

Keystone  filler 94.74 

Ferric  oxide ...               30.511 

Silica  and  silicates ...               12. 971 

Calcium  sulphate,  hydrated    ...          ...  ...               19.12 


100.00  100.00          100.00 

1  Evidently  Princes'  metallic  and  Indian  red. 

The  vehicles  were  judged  to  be  blends  of  grinding 
Japan,  rosin-china  wood-oil  varnish,  and  a  benzine  drier. 

511.  Rough  stuff.  This  product  is  somewhat  similar 
to  iron  filler  in  composition,  but  it  usually  has  a  much 
higher  lead  content  and  therefore  commands  a  better 
price.  The  pigment  portion  is  usually  white  lead,  Key- 
stone or  similar  filler,  and  a  small  percentage  of  lamp- 
black, bone  black,  or  carbon  black.  The  vehicle  is  also 
similar  to  that  used  in  iron  fillers,  except  that  in  the 
better  class  of  rough  stuff  a  fairly  good  grade  of  kauri 
varnish  is  used. 

ANALYSES  OF  ROUGH   STUFF. 

I.  n. 

Per  cent.  Per  cent. 

Keystone  filler 73.181  76.242 

White  lead.  26.82  23.76 


100.00  100.00 

1  Tint  indicated  presence  of  small  amount  of  lampblack. 

2  Contained  considerable  magnesium  silicate;  white  filler  probably 
present. 


CHAPTER  XXVIII. 

SHINGLE  STAINS,  BARN  AND  ROOF  PAINTS. 

512.  Shingle  stains.     The  manufacture  of  really  high- 
grade  shingle  stains  has  been  accomplished  by  only  a 
very  few  paint  firms,  as  the  basis  of  success  is  the  ob- 
taining of  the  right  kind  of  creosote  oil.     There  are  a 
number  of  creosote  oils  on  the  market  which  have  been 
freed  from  naphthalene  sufficiently  so  that  the  naph- 
thalene will  not  separate  out  when  chilled  or  when  the 
prepared  stain  is  subjected  to  cold  weather;  but  it  will 
be  observed  that  such  creosote  oils  will  be  low  in  the 
phenyloid  or  preservative  bodies,  and  therefore  will  ex- 
ert little  preservative  action  toward  the  wood,  or  else 
the  prepared  stain  changes  color  in  the  package.     This 
is  particularly  noticeable  with  the  greens;  the  change 
will  begin  within  a  few  weeks  after  being  prepared  and 
continue  until  the  color  has  gone  over  to  a  dirty  brown. 
A  close  examination  will  show  that  this  change  is  usu- 
ally not  due  to  the  alteration  of  the  chrome  green,  but 
to  the  precipitation  of  a  tarlike  substance  which  forms 
a  coating  over  the  chrome-green  particles  and  destroys 
their  tinting  strength. 

513.  Examination.     It  is  necessary,  if  a  high-strength 
creosote  oil  is  to  be  used,  to  refine  it,  which  has  been 
found  to  be  financially  profitable  to  only  a  few  manu- 
facturers,  and  who  use  all  of    their  product    in   the 
preparation  of  their  own  goods.      The  paint  chemist, 
therefore,  should  not  accept  a  creosote  oil  from  the  dis- 
tillation figures  only,  but  should  conduct  a  practical  try- 

236 


SHINGLE  STAINS,   BARN  AND  ROOF  PAINTS.        237 

out,  noting  any  changes  that  may  take  place  in  a  can 
of  the  prepared  stain,  for  two  to  three  months.  The 
author  has  made  numerous  analyses  of  the  leading 
brands  on  the  market,  but  found  very  little  similarity 
in  the  products  examined.  Some  were  simply  cheap 
linseed-oil  paints  and  much  reduced  with  naphtha,  con- 
taining no  creosote  oil  at  all,  the  majority  contained 
varying  amounts  of  a  weak  creosote  oil,  low  in  phenyl- 
oid  bodies,  possessing  little  preservative  action. 

514.  The  following  analysis  reduced  to  formula  is 
representative  of  a  medium-priced,  fairly  high-grade 
shingle  stain: 

Creosote  oil 10  gal. 

Solvent  naphtha  l 12  gal. 

Paraffine  oil   .    j;  .    ;. 12  gal. 

Linseed  oil     .....    .v 2  gal. 

Asbestine  pulp 9  Ibs. 

Chrome  green,  C.  P 15  Ibs. 

1 A  commercial  mixture  of  benzole,  toluene,  and  xylene. 

515.  Barn  paints,  roof  paints,  fence  paints,  etc.     The 
prices  at  which  these  paints  are  offered  for  sale  preclude 
the  use  of  high-grade  materials  such  as  should  be  used 
in  first-quality  house  paints.     They  are,  however,  usu- 
ally satisfactory  for  the  purpose  intended.     The  same 
methods  of  analysis  as  are  applied  to  house  paints  are 
applicable  to  barn  and  roof  paints.     The  latter,  how- 
ever, usually  offer  numerous  complexities,  and  the  ana- 
lytical results  obtained  must  be  interpreted  with  care 
and  discrimination.     It  is  by  no  means  uncommon  for 
manufacturers  who  label  their  goods  as  to  composition 
to  include,  under  the  term  Japan  drier,  a  large  percent- 
age of  naphtha  or  of  kerosene  oil,  and  under  the  term 
varnish,  various   rosin,  rosin-oil,   cottonseed-oil,   soya- 
bean-oil,  and  corn-oil  preparations.     The  detection  of 
these  various  oils  is  comparatively  easy,  but  the  deter- 


238 


PAINT  AND  VARNISH  PRODUCTS. 


mination  of  the  amounts  present,  especially  of  the  last 
four,  is  largely  a  question  of  judgment  rather  than  of 
exactness. 

516.  Analyses.  The  following  analyses  made  by  the 
author  are  believed  to  be  representative  of  the  combina- 
tions on  the  market: 


I. 

II. 

III. 

IV. 

V. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Pigment  .        .... 

47.1 

44.5 

44.0 

15.1 

42.7 

Vehicle    

51.9 

55.5 

56.0 

84.9 

57.3 

100.0 

100.0 

100.0 

100.0 

100.0 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Vehicle: 

Linseed  oil     .... 

52.5 

29.0 

30.0 

41.4 

31.0 

Rosin  and  rosin  oil  . 

, 

26.0 

30.0 

21.0 

Cottonseed  oil  .    .    . 

16.6 

. 

Water     

12.1 

16.2 

.  .  . 

Benzine  

18.8 

45  .0 

40.0 

42.4 

48.  01 

100.0 

100.0 

100.0 

100.0 

100.0 

1  Includes  kerosene. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Pigment: 

Lead  sulphate    .    .    . 

18.24 

Zinc  oxide 

19.76 

Aluminum  silicate  and 

silica    

15.96 

2.35 

31.81 

20.37 

Calcium  carbonate   . 

13.76 

58.45 

43.89 

79!il 

11.46 

Calcium  sulphate 

.  .  . 

53.62 

Ferric  oxide   .... 

70^28 

24^30 

14.55 

1.20 

20.89 

100.00 

100.00 

100.00 

100.00 

100.00 

CHAPTER  XXIX. 

ANALYSIS  OF  JAPANS  AND  DRIERS. 

517.  At  the  present  time  the  terms  " Japan"  and 
11  drier"  are  interchangeable  and  refer   to  the   same 
line  of  products, — manganese  linoleate,  lead  linoleate, 
resinate  of  manganese,  resinate  of  lead,  or  mixtures  of 
these  compounds.     Originally  Japan  contained  a  con- 
siderable quantity  of  dissolved  resin,   constituting  a 
preparation  that  on  drying  gave  a  film  of  considerable 
hardness  and  lustre,  but  this  distinction  has  largely 
disappeared.     These  compounds  should  not  be  con- 
fused with   baking  Japans,   which  represent   an   en- 
tirely different  class  of  products  and  which  will  not  be 
discussed  at  this  time.     Japans  and  driers  are  usually 
made  by  heating  the  oxides  of  lead  and  manganese  or 
borate  of  manganese  with  linseed  oil  or  the  various 
resins,  and  dissolving  the  melted  mass  in  turpentine, 
benzine  or  mixtures  of  both. 

518.  Determination    of    the    drying    salts.     The   salts 
generally  used  are 

Litharge,  PbO 

Red  lead,  Pb3O4 

Oxide  of  manganese,    Mn02 
Borate  of  manganese,  MnB2O4 
occasionally  Zinc  sulphate,  ZnSO4 

and  Zinc  oxide,  ZnO. 

Weigh  25  grams  of  the  drier  into  a  250  c.c.  Erlen- 
meyer  flask  and  dilute  with  25  c.c.  of  a  mixture  of  equal 
parts  of  benzine  and  turpentine.  Add  50  c.c.  of  dilute 

239 


240  PAINT  AND  VARNISH  PRODUCTS. 

hydrochloric  acid  (1.10  sp.  gr.).  Allow  to  stand  1 
hour,  shaking  thoroughly  at  intervals  of  10  minutes. 
Immerse  the  flask  in  a  beaker  of  hot  water,  at  a  con- 
siderable distance  from  the  flame.  When  the  contents 
of  the  flask  are  hot,  shake  with  a  circular  motion,  avoid- 
ing undue  pressure  in  the  flask.  Allow  to  stand  until 
cool,  so  as  to  be  sure  that  the  drier  has  been  wholly 
dissolved.  Pour  into  a  separatory  funnel,  draw  off 
the  aqueous  layer  into  a  casserole,  wash  the  oil  portion 
twice  with  warm  water,  adding  the  washings  to  the 
casserole  and  evaporate  to  dryness  under  the  hood. 
Dissolve  in  dilute  nitric  acid  with  the  aid  of  heat,  filter 
into  a  250  c.c.  graduated  flask  and  after  washing  thor- 
oughly make  up  to  the  mark. 

519.  Lead.     To  an  aliquot  portion  add  5  c.c.  of  dilute 
sulphuric  acid  and  evaporate  on  the  hot  plate  until 
white  fumes  of  sulphur  trioxide  appear.     Cool,  add 
cautiously  50  c.c.  of  water,  heat  to  boiling,  cool  slightly, 
and  add  50  c.c.  of  alcohol.     Allow  to  stand  one-half 
hour,  filter  onto  a  Gooch  crucible,  wash  with  50  per 
cent  alcohol,  dry,  heat  gently  and  weigh  as  lead  sul- 
phate. 

520.  Manganese.     To  an  aliquot  portion  of  the  sam- 
ple add  5  c.c.  of  sulphuric  acid,  dilute  with  10  c.c.  of 
water,  and  evaporate  on  the  hot  plate  until  all  of  the 
hydrochloric  acid  is  expelled  as  shown  by  copious  evo- 
lution of  sulphur  trioxide  fumes.     Cool,   dissolve  in 
about  25  c.c.  of  water  and  heat  carefully  with  occa- 
sional shaking  until  all  of  the  anhydrous  sulphate  of 
iron  has  dissolved.     Transfer  to  a  250  c.c.  graduated 
flask  and  add  an  excess  of  zinc  oxide  emulsion,  obtained 
by  mixing  C.  P.  zinc  oxide  with  water.     Avoid  a  large 
excess,  but  sufficient  to  precipitate  all  the  iron,  so  that 
on  standing  the  solution  begins  to  settle  clear  and  some 


ANALYSIS  OF  JAPANS  AND   DRIERS.  241 

zinc  oxide  can  be  seen  in  the  bottom  of  the  flask. 
Cool  and  make  up  to  the  mark.  Transfer  an  aliquot 
portion  to  a  beaker  or  flask  and  add  an  excess  of  a  sat- 
urated solution  of  bromine  water,  and  about  3  grams 
of  sodium  acetate.  One  c.c.  of  a  saturated  solution  of 
bromine  water  will  precipitate  about  0.01  gram  of 
manganese.  Boil  about  2  minutes.  Filter  and  wash 
with  hot  water.  The  filtrate  must  be  perfectly  clear. 
Place  the  filter  containing  the  washed  precipitate  back 
in  the  beaker  or  flask  in  which  the  precipitation  was 
made.  All  traces  of  bromine  must  be  entirely  ex- 
pelled. 

Add  an  excess  of  standard  oxalic  acid  solution  and 
about  50  c.c.  of  dilute  sulphuric  acid  (1:9)  and  heat 
nearly  to  boiling  with  gentle  agitation  until  the  pre- 
cipitate is  entirely  dissolved.  Dilute  to  about  200  c.c. 
with  hot  water  and  titrate  with  standard  perman- 
ganate. 

521.  Zinc.     Zinc   sulphate   and   zinc   oxide  are   but 
little  used  at  present  in  driers.     If  present  zinc  may  be 
estimated  in  the  filtrate  from  the  lead  sulphate,  as  de- 
scribed under  the  analysis  of  mixed  paints  containing 
umbers  and  siennas. 

522.  Calculations.     The  color  of  the  drier  gives  a  clue 
as  to  the  combinations  used,  borate  of  manganese  being 
used  in  light  colored  driers,  oxide  of  manganese  in  dark 
driers,"  and  the  oxides  of  lead  in  medium  colored  driers. 
By  far  the  most  common  combination  is  a  mixture  of 
borate  of  manganese  and  litharge. 

523.  Determination  of  the  volatile  oils.     Five  grams  of 
the  drier  are  quickly  weighed  into  a  flat-bottomed  dish 
(a  petri-plate  is  the  most  suitable),  dried  for  3  hours  at 
150°  C.,  cooled  and  weighed.     Loss  in  weight  repre- 
sents very  closely  the  amount  of  volatile  thinner  pres- 


242  PAINT  AND  VARNISH  PRODUCTS. 

ent,  and  in  the  samples  analyzed  by  the  author  the 
volatile  thinners  constituted  63  to  68  per  cent  by 
weight. 

524.  Separation  of  benzine  and  turpentine.     About  100 
grams  of  the  drier  are  distilled  to  the  point  of  incipient 
decomposition,  the  distillate  redistilled  and  the  benzine 
estimated  by  the  Sulphuric  Acid  Number,  as  described 
under  the  analysis  of  volatile  oils. 

525.  Detection  of  rosin.     About  1  c.c.  of  the  drier  is 
dissolved  in  15  c.c.  of  acetic  anhydride,  warming  until 
the  solution  is  complete.     Cool,   filter,   place  a  few 
drops  of  the  filtrate  on  a  crucible  cover  and  add  a  drop 
of  sulphuric  acid,  so  that  it  will  mix  slowly.     If  rosin 
is  present  a  characteristic  fugitive  violet  color  results. 
Linoleate  driers  sometimes  give  a  color  resembling  that 
of  rosin  driers,  and  it  is  better  to  evaporate  a  portion  of 
the  drier  to  a  syrup  consistency,  treat  with  alcohol,  and 
test  the  alcoholic  extract. 

526.  Practical  tests.    The  chemical  analysis  of  a  Japan 
will  give  very  little  information  regarding  its  efficiency, 
since  the  latter  is  largely  dependent  upon  the  condi- 
tions of  manufacture.     The  following  specifications,1  as 
adopted  and  used  by  the  Philadelphia  and  Reading 
Railroad,  give  very  excellent  methods  for  determining 
the  efficiency  of  a  Japan. 

"The  material  desired  consists  of  a  pure  turpentine 
hardener  and  oil  drier,  conforming  to  the  following: 

1st.  When  equal  parts  by  weight  of  the  Japan  and 
of  pure  turpentine  are  thoroughly  mixed  and  poured 
over  a  slab  of  glass,  which  is  then  placed  nearly  vertical 
at  a  temperature  of  100°  Fahrenheit,  with  a  free  access 
of  air,  but  not  exposed  to  draught,  the  coating  shall  be 

1  Practical  Testing  and  Valuation  of  Japan,  by  Robert  Job,  Chem- 
ical Engineer,  Vol.  IV.,  No.  5. 


ANALYSIS  OF  JAPANS  AND   DRIERS.  243 

hard  and  dry,  neither  brittle  nor  sticky,  in  not  exceed- 
ing 12  minutes. 

2d.  When  thoroughly  mixed  with  pure  raw  linseed 
oil  at  the  ordinary  temperature  in  proportions  of  5 
per  cent  by  weight  of  Japan  to  95  per  cent  by  weight 
of  raw  linseed  oil,  no  curdling  shall  result,  nor  any 
marked  separation  or  settling  on  standing. 

3d.  When  the  above  mixture  is  flowed  over  a  slab 
of  glass,  which  is  then  placed  nearly  vertical,  at  a 
temperature  of  100°  Fahrenheit,  with  free  access  to 
air,  but  not  exposed  to  draught,  the  coating  shall  dry 
throughout,  neither  brittle  nor  sticky,  in  not  exceeding 
2  hours. 

4th.  When  five  cubic  centimeters  of  the  Japan  are 
poured  into  95  cubic  centimeters  of  pure  turpentine  at 
the  ordinary  temperature,  and  thoroughly  shaken,  a 
clear  solution  shall  result,  without  residue,  on  standing 
1  hour. 

5th.  After  evaporation  of  the  turpentine,  the  solid 
residue  must  be  hard  and  tough,  and  must  not  'dust' 
when  scratched  with  a  knife. 

6th.  Benzine  or  mineral  oil  of  any  kind  will  not  be 
permitted. 

Shipments  which  are  not  closely  in  accordance  with 
these  specifications,  or  which  are  not  of  uniform  quality 
throughout,  will  be  returned  at  the  expense  of  the 
shipper/' 

527.  The  temperature  of  100°  F.  is  obtained  by  the 
use  of  a  suitable  oven.  The  strips  of  glass  used  being 
4  inches  long  by  2  inches  wide.  They  are  so  placed  in 
the  oven  that  there  is  free  access  of  air,  but  no  draught. 
The  bulb  of  the  thermometer  is  placed  beside  the  glass 
strips  and  the  dryness  of  the  film  tested  opposite  the 
bulb  of  the  thermometer. 


244  PAINT  AND  VARNISH  PRODUCTS. 

The  addition  of  rosin  renders  the  dry  film  brittle  and 
hence  will  "dust"  when  scratched  with  a  knife. 

The  majority  of  driers  used  for  house  and  barn  paints 
are  weak  driers,  and  will  not  meet  the  above  require- 
ments. However,  if  the  chemist  will  test  out  a  few 
high-class  driers  by  the  above  specifications,  he  will 
have  but  little  trouble  in  estimating  the  value  of  the 
cheaper  and  inferior  driers. 

The  United  States  Treasury  specifications  for  man- 
ganese borate  require  that  it  be  free  from  by-products, 
and  that,  other  properties  being  satisfactory,  prefer- 
ence will  be  given  to  the  article  containing  the  least 
amount  of  alkali. 

Another  practical  test  much  in  vogue  among  practi- 
cal painters  and  shop  foremen  is  to  make  a  semi-paste 
with  moisture-free  litharge  and  the  drier.  High-class 
driers  will  remain  three  to  four  days  before  showing  a 
decided  tendency  to  thicken  or  harden;  cheap  rosin 
driers  will  begin  to  harden  in  a  comparatively  short 
time. 


CHAPTER  XXX. 

ANALYSIS   OF   SHELLAC   AND    SPIRIT   VARNISHES. 

Analysis  of  Shellac. 

528.  The  most  common  adulterant  of  shellac  is  com- 
mon rosin  or  colophony.     Sabin,  in  his  Technology  of 
Paint  and  Varnish,  says  that,  "It  is  reported  and  prob- 
ably true,  that  large  quantities  of  common  rosin  are 
shipped  to  India  and  used  as  an  adulterant  of  gum 
shellac." 

529.  Detection  of  rosin.     About  1  gram  of  the  sample 
is  dissolved  in  about  15  c.c.  of  acetic  anhydride,  warm- 
ing gently  until  the  solution  is  complete.     Cool  thor- 
oughly under  the  tap.     The  rosin  will  remain  in  solution 
while  the  greater  part  of  the  shellac  will  separate  out. 
Filter.     Place  a  few  drops  of  the  filtrate  on  a  porce- 
lain crucible,  cover,  and  add  by  means  of  stirring  rod 
one  drop  of  sulphuric  acid  (34.7  c.c.  sulphuric  acid  and 
35.7  c.c.  water)  so  that  it  will  mix  slowly.     If  rosin  is 
present  a  characteristic  violet  fugitive  color  results.    A 
pure  shellac  should  give  no  coloration. 

530.  Estimation  of  rosin.     The  amount  of  rosin  pres- 
ent is  best  estimated  by  means  of  the  iodine  number. 
For  this  purpose  the  Hanus  method  is  to  be  preferred  to 
the  Hubl  or  Wijs  method.     The  Hubl  for  a  long  time 
has  been  the  official  method,  but  it  has  several  faults 
which  affect  its  accuracy.     It  rapidly  loses  strength 
and  is  so  slow  in  its  reaction  with  some  oils,  such  as 
linseed  oil,  that  a  serious  error  is  brought  about  by 

245 


246  PAINT  AND  VARNISH  PRODUCTS. 

the  change  in  strength  of  the  solution  during  the  reac- 
tion. Another  objection  to  the  Hubl  method  is  that 
practically  each  chemist  uses  a  modification  of  his 
own  as  regards  the  time  necessary  for  the  solution  to 
remain  in  contact  with  the  substance  to  be  tested. 

In  their  workings  the  Hanus  and  Wijs  methods  are 
very  similar,  but  the  Hanus  solution  is  much  easier  to 
prepare  and  the  results  obtained  more  nearly  corre- 
spond to  those  obtained  by  the  Hubl  method.  As 
most  of  the  published  data  relating  to  the  iodine  num- 
bers of  oils,  fats,  etc.,  has  been  obtained  by  the  use  of 
the  Hubl  method,  this  fact  is  of  considerable  impor- 
tance in  making  comparisons. 

531.  The  Hanus  solution  is  prepared  and  used  as 
previously  described. 

0.2  gram  to  0.3  gram  of  the  ground  sample  is  intro- 
duced into  a  250  c.c.  Erlenmeyer  flask;  20  c.c.  of 
glacial  acetic  acid  added,  and  the  mixture  warmed 
until  the  solution  is  complete,  except  for  the  wax. 
10  c.c.  of  chloroform  is  added,  the  solution  cooled  to 
room  temperature,  and  25  c.c.  of  Hanus  solution  added, 
the  flask  stoppered,  allowed  to  remain  in  the  dark  or 
in  diffused  light  for  1  hour,  with  occasional  shaking. 
10  c.c.  of  potassium  iodide  solution  and  100  c.c.  of 
water  are  added  and  titrated  with  tenth-normal  thiosul- 
phate,  using  starch  as  an  indicator  in  the  usual  man- 
ner. Blank  determinations  should  be  made  each  time. 

EXAMPLE: 

Wt.  of  sample  =  0.4  gram. 

A  blank  of  25  c.c  of  Hanus  solution  required  55  c.c. 
of  thiosulphate. 

1  c.c.  of  thiosulphate  =  .0125  gram  of  iodine. 
Titration  of  unabsorbed  iodine  =  49.5  c.c.  thiosulpkate. 


ANALYSIS  OF  SHELLAC  AND  SPIRIT  VARNISHES.      247 


55.0  —  49.5  =  5.5  c.c.  of  thiosulphate  equivalent  to 
iodine  absorbed. 

(5.5  X  100  X  .0125)  ^  0.4  =  17.2  per  cent  iodine 
absorbed. 

532.  Iodine  Numbers  of  shellacs  obtained  from  the 
leading  wholesalers  and  jobbers  of  the  United  States, 
supposed  to  be  strictly  pure: 1 


No. 

Variety. 

Iodine  No. 

Color  Reaction^ 

1 

Orange  shellac 

31   06 

Rosin  present 

9 

Unbleached  shellac 

15  85 

Rosin  absent 

3 

Orange  shellac     .                       ... 

12  68 

Rosin  absent 

4 
5 
6 
13 

Ralle  standard  shellac  
Star  brand  shellac  
H.  N.  superior  shellac  
Orange  shellac     

16.80 
14.90 
12.99 
22.27 

Rosin  absent. 
Rosin  absent. 
Rosin  absent. 
Rosin  present 

14 

Orange  shellac  

20.36 

Rosin  absent. 

15 

Orange  shellac 

16  54 

Rosin  absent 

16 

Orange  shellac 

20  36 

Rosin  absent 

17 

Orange  shellac 

13  36 

Rosin  absent 

7 
8 
P 

Bone  dry  bleached  shellac    .... 
Refined  bone  dry  bleached  shellac 
Bleached  shellac  

8.87 
12.34 
6  34 

Rosin  absent. 
Rosin  absent. 
Rosin  absent 

10 

Bleached  shellac.    

8  87 

Rosin  absent 

1?, 

Bleached  shellac  :   .    .    . 

13.36 

Rosin  absent. 

Analysis  of  Shellac  Varnish. 

533.  Composition.  A  varnish  having  the  proper  con- 
sistency is  prepared  by  dissolving  45  parts  of  shellac  in 
55  parts  of  grain  alcohol  of  94  per  cent  strength  or 
about  5  pounds  of  shellac  per  gallon  of  alcohol.  In 
place  of  the  expensive  grain  alcohol,  some  manufac- 
turers substitute  wood  alcohol  or  Columbian  spirits, 
which  is  rectified  wood  aJcohol.  The  poisonous  prop- 
erties of  wood  alcohol  are  well  known,  and  on  account 
of  its  injurious  effects  great  care  should  be  exercised 
in  the  use  of  varnishes  containing  it.  Shellac  varnish 

1  Analyses  by  author. 

2  Libermann-Storch  Reaction. 


248  PAINT  AND  VARNISH  PRODUCTS. 

is  often  adulterated  with  rosin,  thus  producing  a  prod- 
uct of  an  inferior  quality.  The  sophistication  of 
varnish  with  this  substance  is  well  described  by  Lang- 
muir: 1  "Starting  out  with  an  adulterated  shellac,  the 
varnish  maker,  secure  in  his  belief  that  rosin  cannot  be 
detected  in  the  solution,  proceeds  to  add  still  more 
rosin.  What  has  been  said  in  regard  to  adulteration 
of  shellac  fades  into  insignificance  in  comparison  with 
that  practice  in  the  manufacture  of  shellac  varnishes. 
Shellac  varnishes  are  sold  containing  no  shellac.  'Pure' 
shellac  varnishes,  grain  alcohol,  may  be  purchased  at 
less  cost  than  the  alcohol." 

534.  Determination  of  the  body  of  shellac  varnishes. 

3  to  5  grams  of  the  well  stirred  sample  is  weighed 
into  a  weighed  flat-bottom  petri-dish  and  evaporated 
to  a  constant  weight  in  the  steam  oven.  The  result  is 
calculated  in  pounds  per  gallon.  If  a  platinum  evap- 
orating dish  be  used  and  the  evaporation  conducted 
over  a  water  bath,  the  amount  taken  should  not  be 
over  1  gram.  Taking  the  weight  of  a  gallon  of  wood 
alcohol  at  60°  F.  as  6.75  pounds,  the  pounds  per  gallon 
may  be  ascertained  by  means  of  the  following  table: 2 

Per  cent.  Pounds 

Residue.  per  Gallon. 

30.77 3.0 

34.15 3.5 

37.20 4.0 

40.00 4.5 

42.55 5.0 

44.90 5.5 

47.06 6.0 

49.05 6.5 

50.91  .    . 7.0 

52.63 7.5 

54.23 8.0 

1  Determination  of  Rosin  in  Shellac,  J.  Soc.  Chem.  Ind.,  January  1, 
1905. 

2  Ibid. 


ANALYSIS  OF  SHELLAC  AND  SPIRIT  VARNISHES.      249 

535.  Determination  of  the  strength  of  the  alcohol  used. 
The  strength  of  the  alcohol  may  be  calculated,  know- 
ing the  per  cent  of  residue  as  determined  above  and 
the  specific  gravity  of  the  varnish.     The  calculation  is 
best  illustrated  by  the  following  example: 

5  grams  of  varnish  yielded  a  residue  of  2.300  grams. 

The  specific  gravity  of  the  varnish  was  0.9445  at 
15.5°  C. 

100  grams  of  the  varnish  gave  2.300  X  20  =  46.00 
grams  of  residue  or  46.00  per  cent. 

The  alcohol  by  difference  100.00  -  46.00  =  54.00 
grams  or  54.00  per  cent. 

Average  specific  gravity  of  shellac  itself  =  1.145. 

The  volume  taken  up  by  the  shellac  in  the  varnish 
would  be  46.00  -*-  1.145  =  40.17  c.c.  in  100  grams  of 
varnish. 

The  specific  gravity  of  the  varnish  was  0.9445. 

100  c.c.  would  weigh  94.45  grams  and  hence  100 
grams  would  occupy  105.9  c.c. 

105.9  c.c.  —  40.17  c.c.  =  65.73  c.c.,  the  volume  occu- 
pied by  54.00  grams  of  alcohol  solvent. 

54.00  -s-  65.73  =  0.8215,  the  specific  gravity  of  the 
alcohol.  From  the  alcohol  tables  this  will  be  found  to 
correspond  to  90.5  per  cent  of  grain  alcohol.  If  de- 
sired a  portion  of  the  varnish  may  be  distilled  until 
the  decomposition  point  is  reached  and  the  strength  of 
the  alcohol  determined  from  the  specific  gravity  of  the 
distillate. 

536.  Examination  of  the  solvent.     One  hundred  grams 
of  the  varnish  are  carefully  distilled  to  the  point  of  in- 
cipient decomposition.     If  necessary  the  distillate  may 
be  redistilled. 

537.  Detection  of  benzine.     Dilute  a  portion  of  the 


250  PAINT  AND  VARNISH  PRODUCTS. 

distillate  with  three   or  four  volumes  of  water.     If 
benzine  is  present  it  will  separate  but. 

538.  Columbian  spirit  and  wood  alcohol.    The  test  for 
acetone,  which  is  always  to  be  found  in  wood  alcohol, 
will  distinguish  between  Columbian  spirit  and  wood 
alcohol. 

539.  Detection  and  estimation  of  wood  alcohol  in  mix- 
tures  with   grain   alcohol.     Qualitatively,    the    methyl 
alcohol  may  be  detected  by  the  following  method: 

Dilute  a  portion  of  the  distillate  until  the  liquid  con- 
tains approximately  12  per  cent  of  alcohol  by  weight. 

Oxidize  10  c.c.  of  the  liquid  in  a  test  tube  as  follows: 
Wind  copper  wire  1  mm.  thick  upon  a  rod  or  pencil  7  to 
8  mm.  thick  in  such  a  manner  as  to  enclose  the  fixed 
end  of  the  wire  and  to  form  a  close  coil  3  to  3.5  cm. 
long.  Twist  the  two  ends  of  the  wire  into  a  stem  20 
cm.  long  and  bend  the  stem  at  right  angles  about  6  cm. 
from  the  free  end,  or  so  that  the  coil  may  be  plunged 
to  the  bottom  of  a  test  tube,  preferably  about  16  mm. 
wide  and  16  mm.  long.  Heat  the  coil  in  the  upper  or 
oxidizing  flame  of  a  Bunsen  burner  to  a  red  heat 
throughout.  Plunge  the  heated  coil  to  the  bottom  of 
the  test  tube  containing  the  diluted  alcohol.  With- 
draw the  coil  after  a  second's  time  and  dip  it  in  water. 
Repeat  the  operation  from  three  to  five  times,  or  until 
the  film  of  copper  oxide  ceases  to  be  reduced.  Cool  the 
liquid  in  the  test  tube  meanwhile  by  immersion  in  water. 

540.  Add  1  c.c.  of  strong  ammonia  to  the  oxidized 
liquid  in  a  casserole  and  expel  the  acetaldehyde  by 
boiling  gently  over  a  direct   flame  until   the  vapor 
ceases  to  smell  of  ammonia.     Add  2  to  3  drops  of 
strong  hydrochloric  acid  to  set  free  the  formaldehyde 
which  has  been  retained  as  hexamethyltetramin,  and 
bring  the  liquid  momentarily  to  a  boil;   cool  promptly 


ANALYSIS  OF  SHELLAC  AND   SPIRIT  VARNISHES.      251 

by  immersion  of  the  casserole  in  water  and  test  for 
formaldehyde  by  the  modified  resorcin  test,  as  fol- 
lows: 

Add  to  the  liquid  remaining  1  drop  of  a  solution 
containing  1  part  of  resorcin  in  200  parts  of  water,  and 
pour  the  mixture  cautiously  into  a  test  tube  contain- 
ing 3  c.c.  of  concentrated  sulphuric  acid,  holding  the 
tube  in  an  inclined  position  in  such  a  manner  that  the 
two  liquids  shall  not  mix.  Allow  it  to  stand  3  min- 
utes, then  sway  the  tube  slowly  from  side  to  side  in 
such  a  manner  as  to  produce  a  gentle  rotary  motion 
of  the  two  layers.  Persist  in  this  operation,  if  neces- 
sary, for  a  minute  or  more,  using  a  piece  of  white 
paper  for  a  background,  and  producing  only  a  very 
gradual  and  partial  mixing  of  the  acid  and  water. 
Nearly  half  of  the  acid  should  remain  as  a  distinct 
unmixed  layer  at  the  end.  When  methyl  alcohol  is 
present,  the  shaking  causes  the  separation  of  more  or 
less  voluminous  flocks  of  a  very  characteristic  rose-red 
color.  The  appearance  of  colored  zones  or  flocks  of 
other  hues,  even  when  tinged  with  red,  or  of  a  rose-red 
solution  without  flocks,  should  never  be  considered 
proof  of  the  presence  of  methyl  alcohol.  However, 
if  the  flocks  are  reddish  brown,  or  if  the  upper  layer 
has  a  pronounced  red,  it  is  often  well  to  repeat  the 
test. 

By  this  method  for  the  removal  of  acetaldehyde  10 
per  cent  of  methyl  alcohol  may  be  readily  detected, 
and  an  experienced  operator  may  detect  with  certainty 
a  less  amount. 

541.  Quantitatively  the  methyl  alcohol  may  be  esti- 
mated by  the  method  of  Thorp  and  Homes. 

This  method  depends  upon  the  fact  that  in  the  pres- 
ence of  potassium  dichromate  and  sulphuric  acid  in  a 


252  PAINT  AND  VARNISH  PRODUCTS. 

closed  vessel  at  100°,  ethyl  alcohol  is  converted  into 
its  theoretical  equivalent  of  acetic  acid,  while  with 
methyl  alcohol,  the  product  resulting  from  the  oxida- 
tion is  always  carbon  dioxide  and  water.  It  has,  how- 
ever, been  found  that  for  each  gram  of  ethy]  alcohol 
present  in  the  solution  0.01  gram  of  carbon  dioxide 
may  be  formed  and  this  correction  should  be  made  in 
all  determinations. 

The  specific  gravity  is  determined  by  means  of  a 
pycnometer.  The  total  per  cent  of  the  alcohol  is  prac- 
tically the  same  as  the  per  cent  of  ethyl  alcohol  of 
the  same  specific  gravity. 

542.  The  methyl  alcohol  is  determined  by  converting 
it  into  carbon  dioxide  by  means  of  sulphuric  acid  and 
potassium  dichromate  in  the  Knorrs'  apparatus  de- 
scribed under  the  estimation  of  carbon  dioxide  in 
white  lead. 

Weigh  into  the  flask  20  grams  of  potassium  dichro- 
mate, connect  the  apparatus  after  having  weighed  the 
soda-lime  tubes.  Introduce  through  the  stop-cock 
funnel  an  exact  volume  of  the  alcohols  not  to  exceed 
4  grams  of  the  mixed  alcohols,  and  an  amount  of  water 
equal  to  50  c.c.  less  the  number  of  c.c.  of  alcoholic 
solution,  80  c.c.  of  sulphuric  acid  (made  by  diluting 
one  volume  of  concentrated  acid  with  four  volumes  of 
water)  are  added,  well  shaken  and  allowed  to  stand 
18  hours.  Dissolve  10  grams  of  potassium  dichromate 
in  50  c.c.  of  water,  add  through  the  funnel,  then  add 
50  c.c.  of  concentrated  sulphuric  acid  and  heat  the 
contents  of  the  flask  to  boiling  for  about  ten  minutes, 
the  carbon  dioxide  being  carried  off  by  a  current  of 
air  through  the  apparatus.  The  heat  is  now  removed 
and  the  current  of  air  continued  for  a  few  minutes 
longer.  Disconnect  and  weigh  the  soda-lime  tubes. 


ANALYSIS  OF  SHELLAC  AND  SPIRIT  VARNISHES.      25.3 

Calculate  the  methyl  alcohol  from  the  proportion 

1.373  :  1  :  :  wt.  CO2  obtained  :  x 
x  =  wt.  methyl  alcohol, 

the  theoretical  oxidation  of  1  gram  methyl  alcohol 
producing  1.373  grams  of  carbon  dioxide. 

EXAMPLE. 

Specific  gravity  of  sample,        0.7992 
Weight  of  sample  used,  1.0118  grams 

Weight  of  carbon  dioxide,          1.3810  grams 
1.373  :  1  :  :  1.3810  :  x 
x  =  1.006  grams  methyl  alcohol. 
1.0118  :  1.1006  :  :  100  :  y 
y  =  99.4  per  cent  methyl  alcohol. 

543.  If  ethyl  alcohol  is  present,  the  correction  pre- 
viously referred  to,  of  0.01  gram  carbon  dioxide  for 
each  gram  of  ethyl  alcohol,  should  always  be  applied. 
The  weight  of  the  methyl  alcohol  subtracted  from  the 
weight  of  the  mixed  alcohols  (calculated  from  the  sp. 
gr.)   gives  the  weight  of  the  ethyl  alcohol,   approxi- 
mately.    The  weight  obtained  by  0.01  gives  correction 
to  be  deducted  from  the  total  carbon  dioxide,  for  the 
recalculation  of  the  weight  of  methyl  alcohol.     It  is 
obvious  that  a  very  slight  error  is  thus  introduced, 
but  the  writer  believes  that  it  is  so  small  that  it  may 
be  safely  neglected. 

544.  Detection  and  estimation  of  rosin.     The  residue 
remaining  after  the  drying  of  the  varnish  in  the  deter- 
mination of  the  "body"  may  be  used  for  the  detection 
of  rosin  as  described  under  the  examination  of  shellac. 

If  much  rosin  is  present,  it  is  not  safe  to  take  the 
residue  after  evaporation  for  the  quantitative  estima- 
tion as  has  been  shown  by  Langmuir.  "A  little  rosin 


254  PAINT  AND  VARNISH  PRODUCTS. 

(iodine  value  224.3)  was  dissolved  in  alcohol,  evapo- 
rated on  the  water  bath  and  heated  5  hours.  It  then 
showed  a  value  of  148.2.  Similarly,  a  dark  rosin  175.7 
fell  to  131." 

A  quantity  of  the  varnish  sufficient  to  yield  0.2  to  0.4 
gram  of  residue  is  weighed  from  a  small  vial,  provided 
with  a  perforated  stopper  carrying  a  shortened  1  c.c. 
pipette,  into  a  200  c.c.  Erlenmeyer  flask;  the  weight  of 
the  sample  used  being  thus  obtained  by  difference. 
The  sample  in  the  flask  is  carefully  evaporated  at  a 
low  temperature  until  pasty  and  then  dissolved  in  the 
requisite  amount  of  acetic  acid  and  chloroform  and 
the  iodine  number  then  determined  in  the  usual  man- 
ner. The  error  due  to  the  action  of  the  small  amount 
of  alcohol  remaining  in  the  pasty  mass  on  the  thio- 
sulphate  is  negligible. 

In  calculating  the  per  cent  of  rosin  the  iodine  values 
of  150  1  for  rosin,  16  1  for  unbleached  and  11  1  for 
bleached  shellac  may  be  used.  If  other  resins  are 
present,  as  sandarac,  etc.,  these  can  only  be  calculated 
in  the  terms  of  rosin. 

545.  Estimation  of  rosin,  Mannhardt's  method.2  Five 
grams  of  gum  shellac  or  10  grams  of  shellac  varnish  are 
weighed  into  a  casserole  flask,  and  the  solvent  ex- 
pelled on  the  water  bath.  The  residue  is  saponified 
with  alcoholic  potash,  the  alcohol  expelled,  and  the 
residue  taken  up  in  100  c.c.  of  hot  water.  At  this 
point  any  wax  present  may  be  extracted  with  benzine 
(sp.  gr.  730),  the  benzine  evaporated  off,  and  the  resi- 
due weighed. 

The  solution  of  the  soaps  is  treated  with  50  c.c.  ben- 
zine (sp.  gr.  .730),  shaken  vigorously,  and,  before  the 

1  Average  values  obtained  by  author. 

2  Hans  Mannhardt,  Chemist,  Heath  &  Milligan  Mfg.  Co. 


ANALYSIS  OF  SHELLAC  AND  SPIRIT  VARNISHES.      255 


emulsion  has  time  to  separate  out,  add  dilute  sulphuric 
acid  in  slight  excess.  The  shellac  acids  immediately 
coagulate,  and  all  rosin  acids  go  into  the  benzine, 
which  is  readily  separated,  filtered  and  evaporated  in 
a  weighed  beaker.  The  shellac  acids  are  absolutely 
insoluble  in  benzine.  Damar  and  possibly  sandarac 
will  behave  like  rosin. 

546.  Practical  test  for  brewers*  varnish.  Varnishes  for 
brewers '  purposes  should  be  made  from  pure  shellac 
and  grain  alcohol  94  per  cent  strength.  They  may  be 
tested  out  by  varnishing  a  strip  of  wood  6  inches  long 
by  3  inches  wide,  and  a  quarter  of  an  inch  in  thickness, 
and  after  drying  immerse  half  of  the  strip  in  4  per  cent 
alcohol  for  48  hours.  A  varnish  made  from  impure 
shellac  or  alcohol  of  less  than  the  proper  strength  will 
soon  turn  white. 


547- 


ANALYSES  OF  SHELLAC  VARNISHES.1 


No. 

Variety. 

Iodine 
Number. 

Percentage  of 
Gum. 

Calculated  Per- 
centage Rosin. 

18 

Orange  shellac  

40.5 

49.8 

18.3 

19 

Orange  shellac  

13.4 

42.2 

23 
25 

Orange  shellac  
Orange  shellac. 

26.2 
16  2 

37.1 
35  9 

7.62 

26 

Orange  shellac.    .    .    . 

15  2 

21  0 

27 
29 

Orange  shellac  
Orange  shellac  

37.4 
23.3 

13.3 

40.5 

16.0 
5  42 

31 

Orange  shellac 

15  0 

39  8 

20' 
30 
21 
22 

28 

White  shellac  
White  shellac  
White  shellac  
White  shellac  
White  shellac  

40.8 
37.8 
13.3 
16.2 
17.5 

44.1 
22.4 
41.0 
37.6 
42.0 

21.4 
19.3 

1  Analyses  by  author. 

2  Liebermann-Storch  reaction  produces  a  somewhat  different  color  than  that  usually 
given  by  rosin,  hence  these  samples  may  be  adulterated  with  other  gums. 

548.  Damar   varnish.      The   following    specifications 
adopted  by  the  Navy  Department,  May,  1904,  will 


256  PAINT  AND  VARNISH  PRODUCTS. 

serve  for  the  practical  testing  and  valuation  of  damar 
varnish. 

Damar  varnish  must  be  made  from  the  very  best 
quality  of  damar  gum  in  a  solution  containing  at  least 
50  per  cent  of  gum  and  45  per  cent  of  turpentine,  the 
gum  to  be  digested  cold  and  well  settled.  The  varnish 
must  be  as  clear  as  and  not  darker  than  the  standard 
sample,  and  must  be  free  from  benzine,  rosin,  lime,  or 
other  mineral  matter.  Its  specific  gravity  at  60°  F. 
must  be  about  0.950,  and  its  flash  point  between  105° 
and  115°F.  It  must  set  to  touch  in  not  more  than 
20  minutes,  and  when  mixed  with  pure  zinc  oxide 
must  show  a  smooth,  glossy  surface  equal  to  that 
shown  by  the  standard  sample. 

549.  Tests.  Besides  chemical  tests  to  determine  the 
above  qualities,  and  practical  tests  to  determine  its 
qualities  of  finish,  a  board  properly  coated  with  a  mix- 
ture of  zinc  and  the  liquid  will  be  exposed  to  the 
weather  for  a  period  of  1  month,  and  at  the  end  of 
this  time  must  have  stood  exposure  equally  as  well  as 
the  standard  sample.  A  similarly  prepared  sample 
will  also  be  baked  at  250°  F.,  and  must  not  at  this 
temperature  show  any  greater  signs  of  cracking,  blis- 
tering, or  any  other  defects  than  standard  samples 
under  the  same  conditions.  Another  sample,  simi- 
larly prepared,  will  be  exposed  in  a  dark  room  at  ordi- 
nary temperature  for  a  period  of  1  month  and  at  the 
end  of  this  time  must  not  have  turned  darker  to  any 
appreciable  degree  than  the  standard  sample. 


CHAPTER  XXXI. 

ANALYSIS  OF  OIL  VARNISHES. 

550.  Analysis  of  oil  varnishes.  As  stated  by  Hurst, 
"The  analysis  of  oil  varnishes  is  one  of  great  difficulty, 
as  it  is  quite  impossible  to  separate  all  the  ingredients 
from  one  another."  However  in  spite  of  the  unsatisfac- 
tory state  of  our  present  knowledge  of  varnish  analysis, 
a  distillation  and  separation  will  give  an  approximate 
idea  of  the  quantity  and  kind  of  volatile  solvents  used. 
Treating  the  residue  by  Twitchell's  method,  will  give 
approximately  the  amount  of  oil  and  the  amount  of 
gum  present  in  the  varnish  and  an  examination  of  the 
physical  and  chemical  properties  of  the  separated  gum 
may  give  an  approximate  idea  of  its  hardness,  and 
throw  some  little  light  on  its  probable  source.  The 
presence  of  lime,  color  produced  by  the  Liebermann- 
Storch  reaction,  acid  figure  and  iodine  absorption  will 
indicate  the  presence  of  rosin  and  to  some  extent  the 
amount  present.  With  these  tests,  in  conjunction  with 
the  solubility  of  the  separated  gum,  the  original  char- 
acter of  the  varnish,  e.g.,  the  pouring  of  a  portion  of 
the  sample  on  a  sheet  of  glass,  noting  how  it  flows, 
dries,  the  kind  of  film  produced,  its  resistance  to  abra- 
sion, to  moisture,  its  elasticity,  etc.,  and  a  comparison 
made  with  varnishes  of  known  composition  and  similar 
properties,  a  very  shrewd  guess  can  be  made  as  to  how 
the  varnish  under  consideration  must  be  duplicated,  or 
in  other  words,  the  approximate  amounts  of  the  dif- 
ferent gums  required  to  produce  a  similar  product. 

257 


258  PAINT  AND  VARNISH  PRODUCTS. 

551.  On  the  other  hand,  a  proximate  analysis  of  a 
varnish  furnishes  us  with  but  a  small  amount  of  help- 
ful information,  as  the  gloss,  working  qualities,  and 
durability  depend  largely  on  the  quality  of  gum  used, 
the  quality  and  treatment  of  the  oil,  the  quality  of  the 
driers  used,  and  especially  as  to  how  the  varnish  was 
prepared,  as  regards  heat,  method  of  cooking,  ageing, 
filtering,   etc.     On  these  essential  points   a  chemical 
analysis  tells  us  but  little.     That  greater  light  will  even- 
tually be  thrown  on  the  problems  involved,  the  author 
has  not  the  slightest  doubt,  but  meanwhile  interpre- 
tations based  solely  on  chemical  analyses  are  liable  to 
be  more  or  less  misleading;    but  taken  in  connection 
with  physical  tests,  carefully  made,  the  value  of  var- 
nishes can  be  determined  with  considerable  accuracy. 

552.  Specific  gravity.     The  determination  of  the  spe- 
cific gravity  is  of  considerable  importance  and  should 
be  made  with  a  pycnometer  at  15.5°  C. 

553.  Viscosity.     The  determination  of  the  viscosity 
of  a  varnish  will  throw  considerable  light  on  its  work- 
ing qualities.     Any  of  the  standard  types  of  viscosim- 
eters  may  be  used  for  varnish  work,  but  the  Doolittle 
Torsion  Viscosimeter  offers  several  advantages   over 
the  others. 

554.  Separation,  identification,  and    estimation  of   the 
volatile  oils.     Seventy-five  grams  of  a  uniform  sample 
of  the  varnish  is  weighed  into  a  500  c.c.  distilling  flask, 
provided  with  a  tube  leading  very  nearly  to  the  bot- 
tom, the  other  end  of  which  is  connected  with  a  steam 
supply.     The  flask  is  also  provided  with  a  thermom- 
eter, the  bulb  of  which  dips  below  the  surface  of  the 
varnish,  and  the  flask  then  connected  with  a  rather 
long  condenser.     By  means  of  an  oil  bath  the  varnish 
is  heated  to  130°  C.,  and  a  current  of  steam  passed 


ANALYSIS  OF  OIL  VARNISHES.  259 

through,  until  about  500  c.c.  of  water  has  passed  over, 
or  until  the  steam  ceases  to  carry  over  any  more 
volatile  oil.  It  is  advisable  to  collect  the  distillate 
directly  in  a  separating  funnel.  When  the  volatile  oil 
has  completely  settled  out,  the  water  is  drawn  off  and 
the  oil  transferred  to  a  weighed  flask,  weighed,  and  the 
percentage  calculated.  The  aqueous  distillate  will  con- 
tain a  small  quantity  of  the  volatile  oil  equal  to  about 
0.4  gram  per  hundred  c.c.  This  correction  should  be 
made  in  calculating  the  percentage. 
li  The  constituents  of  the  volatile  oil  and  the  amount 
of^petroleum  products  present  may  be  determined  in 
th<5  same  manner  as  in  mixed  paints." 

555.  Separation  of  the  resin  gums  from  the  oil,  Twitch- 
elPs  method.  The  flask  containing  the  residue  of  oil 
and  gum  is  connected  with  a  return  condenser,  150  c.c.  of 
normal  alcoholic  potash  added,  the  flask  heated  care- 
fully on  a  water  bath  to  avoid  bumping  and  finally 
heated  over  a  free  flame  for  about  an  hour.  The 
solution  is  then  cooled  and  separated  from  the  residue, 
which  is  again  treated  with  alcoholic  potash,  and  the 
process  continued  until  as  complete  a  saponification 
as  possible  has  been  made;  usually  a  small  residue  of 
about  1  per  cent  remains.  The  different  alcoholic  so- 
lutions are  united,  neutralized  with  hydrochloric  acid, 
the  excess  of  alcohol  evaporated  off,  and  the  fatty 
acids  and  gums  removed  with  successive  portions  of 
ether.  The  ethereal  solution  is  distilled  to  remove 
the  ether,  a  small  quantity  of  absolute  alcohol  added, 
and  the  flask  again  heated  gently,  the  alcohol  carrying 
off  the  last  traces  of  water.  About  10  volumes  of 
absolute  alcohol  are  added  to  the  dry  gums  and  acids, 
the  solution  being  kept  cold  by  ice  and  dry  hydro- 
chloric acid  gas  is  passed  in  until  the  solution  is  sat- 


260  PAINT  AND  VARNISH  PRODUCTS. 

urated.  This  will  usually  take  from  30  to  45  minutes. 
The  flask  and  contents  are  allowed  to  stand  for  about 
an  hour,  then  diluted  with  about  5  volumes  of  hot 
water,  and  boiled  until  clear;  the  heating  being  con- 
ducted gently  to  avoid  frothing. 

556.  The  contents  of  the  flask  are  mixed  with  a  little 
petroleum  ether,  boiling  below  80°  C.,  and  transferred 
to  a  separating  funnel,  the  flask  being  washed  out  with 
the  same  solvent.     The  petroleum  ether  layer  should 
measure  about  50  c.c.     After  shaking,  the  acid  solu- 
tion is  run  off  and  the  petroleum  ether  layer  washed 
once  with  water,  and  then  treated  in  the  funnel  with 
a  solution  of  2.5  grams  of  potassium  hydroxide  and 
20  c.c.  of  alcohol  in  200  c.c.  of  water.     The  ethylic 
esters  dissolved  in  the  petroleum  ether  will  then  be 
found  to  float  on  top,   the  rosin  acids  having  been 
extracted  by  the  dilute  alkaline  solution  to  form  rosin 
soap.     The  soap  solution  is  then  run  off,  decomposed 
with  hydrochloric  acid,  and  the  separated  rosin  acids 
collected  as  such,  or  preferably  dissolved  in  ether,  and 
the  whole  evaporated  in  a  small  weighed  beaker  on 
the  water  bath.     A  small  quantity  of  absolute  alcohol 
is  added,  and  the  evaporation  repeated.     Finally,  cool 
in  the  desiccator  and  weigh.     This  will  give  approxi- 
mately the  amount  of  gums  present  in  the  varnish. 
Any  residue  insoluble  in  the  10  volumes  of  absolute 
alcohol  above  mentioned  is  weighed  up  and  its  weight 
added  to  the  weight  of  resin  gum. 

557.  Separation    of    the    gums    from    the    oil,    Scott's 
Method.1     In  separating  the  gum,  by  this  method,  it  is 
necessary  to  know  whether  the  sample  is  a  Long  Oil  or 
Short  Oil  Varnish,  i.e.,  whether  it  contains  a  large  or 
small  amount  of  linseed  oil.     Hard  oil  finishes,  inte- 

1  Drugs,  oils,  and  paints,  XV.,  No.  4,  page  132,  and  No.  6,  page  219. 


ANALYSIS  OF  OIL  VARNISHES.  261 

rior  varnishes,  and  rubbing  varnishes  are  usually  short 
oil  varnishes,  while  carriage  and  similar  varnishes  are 
long  oil  varnishes. 

In  order  to  determine  to  which  class  a  varnish  be- 
longs, about  10  c.c.  of  the  sample  is  poured  into  a 
beaker  and  50  c.c.  of  benzine,  previously  cooled  to 
about  5°  C.,  added.  If  the  sample  be  short  oil  varnish 
the  gums  will  be  partially  precipitated,  while  a  long 
oil  varnish  will  show  but  little  change.  The  color  of 
the  precipitated  gum  may  be  considered  as  another 
indication,  a  light  colored  precipitate  denoting  a  short 
oil,  and  a  dark  colored  precipitate,  a  long  oil  varnish. 

558.  Short  oil  varnishes.     A  beaker  of  about  150  c.c. 
capacity,   provided   with   a  stirring  rod,   is   carefully 
weighed,  and  about  10  grams  of  varnish  weighed  into 
it.     Cool  to  below  10°  C.     Fifty  c.c.  of  petroleum  ether 
that  has  previously  been  cooled  to  below  3°  C.  is  poured 
into  the  beaker  and  the  contents  stirred.     The  beaker 
is  placed  in  a  freezing  mixture  for  about  an  hour,  or 
until  the  precipitated  gums  have  settled.        «^L,  we^ 

559.  Place  a  filter  paper  that  has  been  dried^in  the 
oven,  in  the  suction  funnel.     Moisten  and  suck  the 
filter  free  from  surplus  moisture,  pour  in  the  gasoline, 
retaining  as  much  of  the  resins  as  possible  in  the 
beaker.     Add  another  50  c.c.  of  ice  cold  petroleum 
ether,  and  allow  to  stand  as  before  on  the  freezing 
mixture.     Meanwhile  pour  25  c.c.  of  ice  cold  water 
on  the  filter  paper,  allowing  it  to  run  into  the  petro- 
leum ether  filtrate,  which  is  then  vigorously  shaken  up 
so  as  to  thoroughly  mix  the  water  and  petroleum 
ether,  which  causes  the  gum  held  in  solution  by  the 
ether  to  precipitate,   and   on  refiltering  is  retained. 
The  second  ether  solution  that  has  been  cooling  is  now 
poured  on  to  the  filter  along  with  the  precipitate,  rins- 


262  PAINT  AND'VARNISH  PRODUCTS. 

ing  out  the  beaker  with  ice  cold  petroleum  ether. 
Treat  with  25  c.c.  of  ice  cold  water,  shaking  and  refilter- 
ing,  as  described  above.  Repeat  this  operation  twice, 
transfer  the  filter,  and  precipitate  to  the  weighed 
beaker,  and  dry  in  the  hot  air  oven  at  105°  to  115°  C. 
and  weigh.  Increase  in  weight,  over  that  of  the  beaker, 
stirring  rod  and  filter,  represents  the  weight  of  the 
gum. 

The  petroleum  ether  solution  containing  the  varnish 
oils  is  poured  into  a  weighed  beaker,  the  excess  of  pe- 
troleum ether  evaporated  off  with  due  precautions, 
and  the  beaker  placed  in  the  hot  air  oven  for  3  hours 
at  150°  C.,  cooled  and  weighed.  The  residue  repre- 
sents the  fixed  oils  in  the  varnish. 

560.  Long  oil  varnishes.     Distil  off  the  thinners  from 
a  portion  of  the  sample.     Weigh  out  10  grams  of  the 
gum  and  oil  into  a  weighed  beaker  as  described  above, 
cool  down  below  15°  C.  and  add  50  c.c.  of  petroleum 
ether  cooled  below  0°  C.     Set  in  the  freezing  mixture 
for  an  hour  and  finish  exactly  as  described  under  short 
oil  varnishes.     The  separation  of  the  total  gum  in 
long  oil  varnishes  is  quite  difficult  and  requires  con- 
siderable patience  and  experience.     According  to  the 
experience  of  the  author,  Scott's  method  gives  some- 
what low  results,  especially  as  rosin  is  quite  soluble  in 
cold  petroleum  ether. 

561.  Determination    of    the    so-called    insoluble    and 
soluble  gums.    This  method  is  somewhat  similar  to  the 
above,  and,  in  the  hands  of  a  careful  chemist,  when  run 
alongside  of  standard  varnishes,  will  throw  consider- 
able light  on  the  nature  of  the  sample  in  question. 

Weigh  2  grams  of  the  sample  into  a  weighed  6-oz. 
wide-mouth  flask,  add  2  c.c.  of  chloroform,  100  c.c.  of 
80°  petroleum  ether,  gradually  and  with  constant  shak- 


ANALYSIS  OF  OIL  VARNISHES.  263 

ing  so  as  to  avoid  any  precipitation,  until  15  c.c.  are 
added,  allow  to  stand  over  night.  The  precipitated 
gums  adhere  to  the  bottom  of  the  flask.  Decant  and 
wash  with  a  little  petroleum  ether.  Dry  to  constant 
weight  as  insoluble  gum. 

The  petroleum  ether  extract  should  be  decanted 
into  a  weighed  beaker,  the  petroleum  ether  evapo- 
rated off  and  the  beaker  dried  at  100°  for  seven  to 
eight  days  to  constant  weight.  All  linseed  oil  should 
now  be  in  the  form  of  linoxyn.  Digest  over  night 
with  chloroform,  which  will  dissolve  the  gum,  and 
leave  the  linoxyn  undissolved.  Filter  through  cotton 
wool.  Evaporate  off  the  chloroform,  dry  to  constant 
weight  in  the  steam  oven  and  weigh  as  soluble  gum. 

A  varnish  to  meet  with  the  requirements  of  the 
United  States  Treasury  Department,  among  other 
things,  should  contain  not  less  than  25  per  cent  of 
best  quality  imported  gums,  and  must  not  contain 
rosin  or  petroleum  products. 

Varnishes  containing  wood  oil  are  liable  to  give  mis- 
leading results  by  the  above  method,  as  the  whole  or  a 
considerable  portion  of  the  wood  oil  will  be  precipitated 
by  the  petroleum  ether,  depending  on  the  length  of 
time  and  temperature  to  which  the  oil  has  been  heated. 

562.  Detection  and  estimation  of  rosin  in  varnishes. 
Qualitatively  rosin  may  be  detected  as  follows:  Pour 
about  5  c.c.  of  the  varnish  into  a  small  separatory 
funnel,  add  about  5  c.c.  of  carbon  bisulphide,  shake 
and  add  10  c.c.  of  acetic  anhydride.  Allow  to  stand 
until  complete  separation  takes  place.  Draw  off  the 
lower  layer,  which  is  the  acetic  anhydride.  Pour  1  or 
2  c.c.  of  the  acetic  anhydride  portion  into  an  inverted 
crucible  cover,  add  carefully,  by  means  of  a  stirring 
rod,  one  drop  of  sulphuric  acid  (34.7  c.c.  of  sulphuric 


264 


PAINT  AND  VARNISH  PRODUCTS. 


acid  to  35.7  c.c.  of  water)  to  the  edge  of  the  cover,  so 
that  it  will  mix  slowly  with  the  acetic  anhydride,  if 
rosin  is  present  a  characteristic  fugitive  violet  color 
will  result. 

563.  The  quantitative  estimation  of  rosin  in  the 
presence  of  other  varnish  gums  is  a  problem  of  especial 
difficulty.  Gill,1  suggests  a  method  based  on  compara- 
tive ester  values.  The  ester  value  being  obtained  by 
subtracting  the  free  acid  value  from  the  saponification 
value.  The  gums  are  separated  from  the  oils  by 
Twitchell's  method,  the  last  traces  of  moisture  being 
removed  by  drying  over  sulphuric  acid.  Gill  obtains 
the  following  values  for  rosin  and  kauri. 


Gum. 

Saponifica- 
tion. 

Free  Acids. 

Ester. 

Average. 

Pure  rosin, 

No.  1 

182  3 

160  1 

22  2 

Pure  rosin, 

No.  6    

185.7 

161.7 

24  0 

23.1 

Kauri,  No 

1 

124  2 

41  0 

83  2 

Kauri,  No. 

2 

129  7 

45  0 

84  7 

84  0 

By  the  use  of  the  usual  formula 

100  (7  -  n) 
m  —  n 


x 


the  percentage  of  adulteration  may  be  approximated, 
as  described  in  the  chapter  on  the  Analysis  of  the 
Vehicle,  in  discussing  cotton-seed  oil. 

564.  Gill's  method  is  open  to  considerable  criticism, 
as  he  directs  that  the  Free  Acid  Value  be  obtained  by 
direct  titration,  and  the  Saponification  Value  by  sapon- 
ifying in  practically  an  open  flask.  Dietrich 2  has 
shown  that  direct  titration  gives  acid  values  far  too 
low  for  all  resin,  because  the  complete  neutralization 

1  J.  Amer.  Chem.  Soc.,  XXVIII.,  No.  12,  page  1723. 

2  Analyse  der  Harze,  Balsane,  und  Gumminharze. 


ANALYSIS  OP  OIL  VARNISHES.  265 

of  the  rosin  acid  proceeds  slowly.  As  an  illustration 
of  this  point,  Worstall 1  gives  the  following  experiment. 
11  Several  portions  of  a  sample  of  kauri,  whose  acid 
number  has  been  accurately  determined  as  103,  were 
weighed  out  and  the  acid  number  determined  by  in- 
direct titration  at  different  intervals  of  time.  The 
results  were  as  follows: 

Time.  Acid  No. 

5  minutes 82 

1  hour 92 

3  hours 96 

6  hours 101 

12  hours 102 

18  hours 103 

565.  Regarding  open  saponification  Worstall  states 
that  "from  the  researches  of  Tschirch  and  his  pupils,  it 
appears  that  the  copals  consist  of  'resenes'  —  neutral 
compounds  containing  oxygen  and  possibly  of  an  alde- 
hyde nature  —  and  of  the  resin  acids.  Other  investi- 
gators have  noted  the  fact  that  the  copals  will  absorb 
oxygen,  and  evidently  the  increase  in  acid  number 
and  decrease  in  iodine  absorption  is  due  to  the  oxida- 
tion of  these  'resenes/  by  contact  with  the  air,  to  resin 
acids.  .  .  .  That  this  increase  in  the  acid  number  is 
actually  due  to  oxidation,  the  following  experiments 
will  illustrate: 

'  "A  number  of  samples  of  Kauri  were  selected,  each 
one  finely  powdered,  and  its  acid  and  iodine  numbers 
determined.  These  samples  were  then  left  four  months 
in  open  bottles  exposed  to  the  air,  and  the  powdered 
resins  stirred  from  time  to  time  to  promote  oxidation. 
At  the  end  of  this  time  their  constants  were  again  de- 
termined with  the  following  results. 

1  Chemical  Constants  of  Fossil  Resins,  J.  A.  Chem.  Soc.,  XXV.,  page 
860. 


266 


PAINT  AND  VARNISH  PRODUCTS. 


No. 

Before 
Acid. 

Oxidation 
Iodine. 

After 
Acid. 

Oxidation 
Iodine. 

Acid 
Increase. 

Iodine 
Decrease. 

1 

72 

154 

87 

133 

15 

21 

2 

76 

159 

111 

121 

35 

38 

3 

77 

140 

93 

115 

16 

25 

4 

72 

170 

107 

110 

35 

60 

5 

97 

109 

104 

99 

7 

0 

6 

105 

113 

109 

112 

4 

1 

" Samples  1,  2,  3  and  4  were  hard,  'bold'  gum  of 
highest  quality,  while  samples  5  and  6  were  of  a  soft, 
spongy,  lowest  grade  Kauri,  in  which  oxidation  had 
already  made  much  progress  before  the  experiment 
was  carried  out. 

"This  oxidation  proceeds  rapidly  in  presence  of  alka- 
lies, so  that  open  saponification  with  alcoholic  caustic 
potash  gives  acid  numbers  that  are  much  too  high. 
Doubtless  this  fact,  in  connection  with  the  impossi- 
bility of  obtaining  correct  acid  numbers  by  direct  titra- 
tion,  has  led  to  the  reporting  of  ester  values  in  resins 
where  no  esters  exist.  That  Kauri  is  free  from  esters 
was  shown  by  saponifying  several  samples  in  flasks 
with  return  condensers,  digesting  for  one  hour  on  the 
steam  bath.  In  every  case  the  saponification  number 
thus  found  was  the  same  as  the  indirect  acid  number." 

566.  From  the  above  data  it  is  evident  that,  in  order 
to  approximate  the  percentage  of  rosin  in  a  varnish  by 
the  so-called  ester  values  according  to  Gill's  method, 
each  analyst  must  establish  his  own  set  of  figures, 
under  certain  definite  working  conditions,  obtaining  his 
data  from  varnishes  of  known  composition.  Any  vari- 
ation of  these  conditions,  either  in  time,  factor  or  con- 
dition of  the  gums,  is  certain  to  give  different  results. 

Little  that  is  reliable  has  been  written  concerning 
the  detection  of  the  other  varnish  gums.  Certain 


ANALYSIS  OF  OIL  VARNISHES.  267 

resins,  however,  give  some  indication  of  their  presence. 
For  instance,  Kauri  imparts  a  reddish  stain  to  a  var- 
nish. Damar,  if  present  in  considerable  quantity,  can 
be  detected  by  its  smell,  especially  in  the  dried  var- 
nish. It  is  seldom  found  in  varnishes  intended  for 
outside  use. 

567.  In  closing,  a  word  should  be  said  concerning 
wood  oil.     This  product,  the  properties  of  which  are 
but  little  understood  by  the  majority  of  chemists,  is 
finding  a  wide  use  among  varnish  manufacturers.     It 
is  claimed  by  varnish  manufacturers  that  by  the  use 
of  wood  oil,  varnishes  containing  a  large  amount  of 
rosin  may  be  prepared,  possessing  satisfactory  wear- 
ing qualities  and  free  from  the  objectionable  features 
of  ordinary  rosin  varnishes.     However,  in  light  of  the 
rather  heavy  losses  encountered  by  a  number  of  var- 
nish firms  in  endeavoring  to  prepare  a  satisfactory 
rosin-wood  oil  varnish,  the  above  claims  of  the  varnish 
manufacturers  may  be  questioned  somewhat.     As  to 
the  analysis  of  this  type  of  varnish  the  author  is  not 
aware  of  any  suitable  published  method.     It  is  said, 
however,   that  it  may  be  detected  qualitatively  by 
practical  varnishers,  in  quantities  as  low  as  five  per 
cent  by  the  characteristic   odor  given  off  in  sand- 
papering a  coat  which  has  barely  dried. 

568.  Navy  specifications  for  interior  varnish  for  naval 
vessels,  1906.     To  be  of  the  best  quality  and  manu- 
facture and  equal  in  all  respects  —  including  body, 
covering  properties,  gloss,  finish  and  durability  —  to 
the  standard  samples  in  the  general  storekeeper's  office, 
navy  yard,  New  York.     To  be  made  exclusively  from 
the  best  grade  of  hard  varnish  resins,  pure  linseed  oil, 
pure  spirits  of  turpentine  and  lead  manganese  driers, 
and  to  be  free  from  all  adulterants  or  other  foreign 


268  PAINT  AND  VARNISH  PRODUCTS. 

materials.  The  varnish  must  flash  above  105°  F.,  set 
to  touch  in  from  6  to  8  hours,  and  dry  hard  within  24 
hours  in  a  temperature  of  70°  F.  It  must  stand  rub- 
bing with  pumice  stone  and  water  within  36  hours 
without  sweating,  and  must  polish  in  72  hours  with 
rotten  stone  and  water.  To  be  as  clear  and  not  darker 
than  the  standard  sample,  and  to  be  equal  to  it  in  all 
respects  as  above  specified. 

569.  Navy  specifications  for  black  asphaltum  varnish, 
1906.  Black  asphaltum  varnish  must  be  of  pure,  high- 
grade  asphaltum  of  the  very  best  quality,  pure  linseed 
oil,  pure  spirits  of  turpentine  and  lead  manganese 
driers,  and  to  be  free  from  all  adulterants  or  other 
foreign  materials,  and  must  contain  not  less  than  20 
gallons  of  prepared  linseed  oil  to  100  gallons  of  varnish. 
It  must  not  flash  below  105°  F.  (open  tester).  It 
must  mix  freely  with  raw  linseed  oil  in  all  proportions ; 
must  be  clear  and  free  from  sediment,  resin,  and 
naphtha,  when  flowed  on  glass,  and  allowed  to  drain 
in  a  vertical  position;  the  film  must  be  perfectly 
smooth  and  of  full  body.  It  must  set  to  touch  in 
from  If  to  2  hours,  and  dry  hard  in  less  than  20  hours 
at  70°  F.  When  dry  and  hard  it  must  not  rub  up  or 
powder  under  friction  by  the  finger.  The  applica- 
tion of  heat  must  quicken  the  time  of  drying  and  give 
a  harder  film. 


CHAPTER   XXXII. 

THE  PRACTICAL  TESTING   OF  VARNISHES. 

570.  The  thorough  practical  testing  of  varnishes  is  an 
exceedingly  difficult  matter  for  the  average  chemist,  as 
it  requires  long  familiarity  with  the  direct  application 
of  varnishes  under  a  large  variety  of  circumstances  and 
conditions.     However,  there  are  several  practical  tests 
which   can  be  made  without  special  difficulty,   and 
which  will  throw  considerable  light  on  the  character  of 
the  varnish,  especially  if  the  chemist  be  supplied  with 
a  standard  set  of  varnishes  which  he  can  run  along 
with  the  sample  to  be  tested,  and  have  constantly  by 
him  to  enable  him  to  check  up  his  judgment  by  com- 
parison. 

571.  Smell.     The  smell  of  a  varnish  will  often  tell 
much    concerning    its    value.     A    good,    wholesome, 
gummy  odor  usually  indicates  a  varnish  made  from 
good  materials,  while  a  strong,  raw,  pungent  odor  is 
often,  the  sign  of  a  cheaper  grade  of  goods.     Markedly 
inferior  articles  can  almost  without  exception  be  de- 
tected in  this  manner.     Occasionally  the  true  odor  of 
the  varnish  is  masked  by  a  strong  turpentine  odor,  in 
which  case  allow  a  sample  of  the  varnish  to  drain  out 
of  a  beaker  for  3  to  5  minutes  and  then  note  the  smell 
of  the  portion  adhering  to  the  sides  of  the  beaker,  i.e., 
the  "after  smell,"  as  it  is  called. 

572.  Consistency.     The   consistency  of  a  varnish  is 
to  a  considerable  degree  regulated  according  to  the 
work  for  which  it  is  to  be  used,  and  should  be  judged 

269 


270  PAINT  AND  VARNISH  PRODUCTS. 

accordingly.  There  is  a  marked  tendency,  at  the 
present  time,  to  make  varnishes  altogether  too  thin. 
This  may  in  part  be  due  to  the  insistent  demands 
made  by  contractors  and  other  varnish  users  for  goods 
that  will  "work  fast"  and  dry  quickly,  but  it  should 
be  remembered  that  such  varnishes  do  not  afford  the 
measure  of  protection  to  the  surface  that  is  regarded 
necessary  by  the  best  practical  users  of  varnish. 

573.  Working   and   flowing.     The    working    qualities 
of  the   varnish  under  the  brush  will   at   once  show 
whether  the  chemist  is  dealing  with  a  "long  oil"  or  a 
"short  oil"  varnish.     A  test  board  having  been  suit- 
ably surfaced  and  filled  either  with  thin  shellac,  or  with 
the  varnish  reduced  with  25  per  cent  of  turpentine, 
dried  and  sandpapered  down  smooth,  is  given  an  even, 
uniform  coat  of  the  varnish  to  be  tested.     The  length 
of  time  the  varnish  can  be  worked  under  the  brush, 
before  it  exerts  a  characteristic  "pull"  on  the  brush,  is 
indicative  of  the  character  of  the  varnish.     If  it  per- 
mits of  sufficient  time  for  thorough  brushing  out  so 
that  a  large  panel  could  be  coated  and  worked  out 
smooth,  before  it  begins  to  pull  on  the  brush,  i.e., 
"set  up,"  the  sample  would  be  considered  a  long  oil 
varnish,  while  if  it  begins  to  pull  under  the  brush 
almost  at  once,  it  would  be  considered  a  short  oil 
varnish.     Naturally,  there  are  varnishes  which  do  not 
exhibit  these  extremes,  but  usually  the  classification 
can  be  made  without  difficulty. 

574.  Special  notice  should  be  taken  of  the  way  the 
varnish  flows  out  into  a  uniform  surface,  whether  it 
does  so  with  ease,  or  slowly  and  with  difficulty.     In 
applying  the  final  coats  the  working  and  flowing  can 
be  studied   with  greater  exactness.     Some  varnishes 
will   work   easily,    others   will   work   "tough,"   some 


THE  PRACTICAL  TESTING   OF  VARNISHES.        271 

" greasy/'  etc.;  with  a  little  experience  the  chemist  can 
grade  them  with  considerable  accuracy.  As  men- 
tioned in  a  preceding  paragraph,  there  are  many  var- 
nishes on  the  market  which  are  altogether  too  thin. 
Such  varnishes  will  work  and  flow  with  great  ease 
because  of  their  excessive  thinnessr  and  hence  the  con- 
sistency must  be  taken  into  account  when  passing  on 
the  working  and  flowing  qualities. 

575.  Time  of  drying.     The  time  a  varnish  requires 
to  dry  properly,  i.e.,  to  harden  thoroughly,  is  regulated 
according  to  the  purpose  for  which  the  varnish  is  to  be 
used.     For  instance,  floor  varnishes  are  supposed  to 
dry  hard  over  night,  while  the  average  spar  varnish 
will  require  a  much  longer  time.     Hence  the  samples 
tested  should  be  compared  with  the  accepted  standards 
of  those  types  of  varnishes,  both  on  the  wood  test  sur- 
face and  on  a  sheet  of  glass,  on  which  samples  of  the 
varnishes  have  been  placed  and  then  set  in.  a  dust-free 
but  unconfined  place  at  an  angle  of  about  30  degrees 
from  the  perpendicular.     The  best  results  are  secured 
by  resting  the  glass  on  a  couple  of  small  hooks,  which 
permits  the  varnish  to  drain  freely.     The  rapidity  of 
the  drying  should  be  noted  at  regular  intervals.     When 
dry,  the  tests  should  be  saved  for  further  examination. 

576.  The  sponge  test.     After  the  requisite  number  of 
coats  have  been  applied  to  the  test  boards  and  the 
finishing  coat  has  hardened  thoroughly,  a  sponge  made 
of  several  thicknesses  of  felt  is  thoroughly  moistened 
and  laid  on  the  varnished  surface  and  allowed  to  re- 
main for  a  stated  number  of  hours  undisturbed.     A 
high-grade  varnish  will  either  show  no  discoloration 
at  all,  or  will  regain  its  color  on  drying,  provided,  of 
course,  that  it  has  been  suitably  applied.     A  varnish 
containing  a  large  amount  of  rosin  will  be  more  or  less 


272  PAINT  AND  VARNISH  PRODUCTS. 

badly  corroded,  and  will  remain  permanently  white 
and  discolored.  With  a  little  practice  by  working 
with  varnishes  of  known  composition  the  chemist  can 
make  a  pretty  shrewd  guess  as  to  the  approximate 
amount  of  rosin  present  by  the  degree  of  discoloration. 
Right  here  the  author  wishes  to  state  that  the  use  of 
cheap  inferior  rosin  varnishes  has  caused  untold  dam- 
age. There  is  probably  more  rosin  varnish  sold  than 
all  other  grades  put  together.  It  is  claimed  by  high- 
class  manufacturers  that  the  addition  of  three  or  four 
per  cent  of  hardened  rosin  will  enable  the  varnish 
maker  to  melt  his  gums  at  a  somewhat  lower  heat  and 
without  darkening,  thus  making  a  better  and  lighter- 
colored  varnish;  but  the  addition  of  rosin  has  passed 
this  point  so  far  that  a  three  or  four  per  cent  addition 
is  a  very  minor  consideration  indeed. 

577.  Another   modification  of  the  above  test  is  to 
varnish  a*  clean  strip  of  tin,  and  after  thorough  drying 
immerse  it  under  water  and  note  the  rapidity  and  ex- 
tent of  corrosion  and  discoloration. 

578.  Toughness  and  elasticity.     In  order  for  a  varnish 
to  be  durable  and  give  entire  satisfaction,  it  must  have 
the  desired  toughness   and  elasticity  as  well  as  the 
requisite  hardness.     A  varnish  which  is  brittle,  although 
it  may  have    the  required  hardness,   will  be  easily 
cracked  or  crushed  by  a  very  moderate  blow.     Some 
varnishes  are  required  to  be  tougher  and  more  elastic 
than  others,  as  in  the  case  of  floor  finishes. 

579.  The  varnish  having  thoroughly  dried  on  the 
test  glass  alongside  of  the  standard  sample,  its  tough- 
ness may  be  determined  to  a  certain  extent  by  its  be- 
havior under  the  thumb-nail,  and  the  results  obtained 
compared  with  a  similar -examination  on  the  varnish 
test  board.  "Also  the  films  of   the  thoroughly  dried 


THE  PRACTICAL  TESTING   OF  VARNISHES.        273 

varnish  on  the  test  glass  may  then  be  scratched  with  a 
sharp  instrument.  A  small,  sharply  pointed  knife- 
blade  is  excellent  for  this  purpose.  A  first-class  var- 
nish having  suitable  toughness  and  elasticity  will  show 
a  smooth,  even  scratch,  no  scaling  or  "  dusting "  being 
observable;  and  if  the  knife  be  held  in  the  proper 
position,  a  small,  uniform,  coherent  ribbon  of  varnish 
will  be  ploughed  off.  If  the  varnish  is  deficient  in 
elasticity  and  toughness,  it  will  scale  away  under  the 
knife-point,  exhibiting  a  ragged,  irregular  scratch. 
Varnish  films  containing  rosin  when  tested  with  the 
knife-point  will  usually  "dust"  more  or  less  badly,  i.e., 
fly  away  from  the  knife-point  in  the  form  of  a  fine 
powder,  settling  on  the  glass  at  a  considerable  distance 
from  the  scratch.  The  fact  that  varnishes  vary  greatly 
in  consistency  should  be  taken  into  account  in  making 
these  tests,  as  the  films  on  the  glass  will  vary  in  thick- 
ness according  to  the  consistency  of  the  varnish. 

580.  In  judging  the  brittleness  of  a  varnish  on  a 
test  board,  especially  if  it  is  hardwood,  the  effect  of  the 
material  used  for  the  first  coat  must  be  taken  into  con- 
sideration. This  may  be  readily  shown  by  taking  a 
hardwood  board,  coating  a  portion  of  it  with  shellac, 
another  portion  with  an  average  cheap  liquid  filler, 
and  the  remaining  portion  with  the  varnish  itself. 
A'fter  applying  two  coats  of  varnish  over  the  entire 
surface  and  allowing  it  to  harden  thoroughly,  it  will  be 
found  on  testing  the  surface  with  a  knife  that  the 
varnish  over  the  liquid  filler  is  very  brittle,  that  over 
the  shellac  somewhat  brittle,  while  the  straight  varnish- 
filled  surface  will  remain  tough  and  elastic.  Another 
method  of  testing  the  elasticity  is  to  varnish  a  strip  of 
tin,  and,  after  thorough  drying,  bend  the  tin  and  note 
the  extent  which  the  varnish  gives  under  the  strain  to 


274  PAINT  AND  VARNISH  PRODUCTS. 

which  it  is  subjected.  In  making  these  various  tests, 
the  chemist  must  be  certain  that  the  varnish  is  thor- 
oughly dry,  as  many  of  the  cheaper  varnishes  harden 
slowly,  and,  if  examined  too  soon,  will  show  greater 
toughness  and  elasticity  than  would  be  obtained  in 
actual  practice. 

581.  Hardness.  A  varnish  may  have  the  toughness 
and  elasticity  required  of  first-class  goods,  but  may  be 
deficient  in  hardness.  In  order  to  report  on  the  hard- 
ness, the  chemist  should  have  some  means  of  giving 
this  quality  a  numerical  value.  An  instrument  for 
this  purpose  has  been  devised  by  Dr.  A.  P.  Laurie  and 
F.  G.  Baily  of  Heriot  Watt  College,  Edinburgh,  the 
essential  features  of  which  are  a  central  rod  sliding 
easily  in  a  vertical  direction  through  holes  in  two 
brackets.  The  upper  portion  of  the  rod  has  a  screw 
thread,  on  which  is  a  running  nut.  By  means  of  a 
milled  head  at  the  top  the  rod  is  twisted  round,  and 
the  nut  caused  to  travel  up  and  down  on  the  thread. 
A  spring  is  attached  at  its  upper  end  to  the  travelling 
nut  at  the  lower  end  to  the  lower  bracket.  To  the 
lower  end  of  the  rod  is  attached  a  hardened  blunt  steel 
point,  and  the  varnished  plate  to  be  tested  is  placed 
under  this  point,  and  the  point  brought  to  the  surface 
of  the  varnish.  The  test  surface  is  drawn  slowly  under 
the  point,  the  pressure  being  increased  until  a  white 
scratch  is  observed,  at  which  point  the  reading  is 
noted  on  the  scale.  The  machine  reads  to  a  maxi- 
mum of  2000  grams.  Spirit  varnishes  break  down  at 
a  pressure  of  about  100  grams,  rosjn  varnishes  200  to 
400  grams,  fairly  good  common  varnishes  at  about  700 
grams,  and  fine  carriage  varnishes  at  1200  grams  and 
upwards.  The  inventors  claim  that  the  best  oil  var- 
nishes take  twelve  months  to  reach  their  maximum 


THE   PRACTICAL  TESTING  OF  VARNISHES.        275 

hardness,  and  that  the  rate  of  drying  and  the  ultimate 
hardness  can  be  measured  with  accuracy  by  their 
instrument. 

582.  Classification  of  varnishes.     The  varnish  indus- 
try 'has  from  its  beginning  been  conducted  with  as 
much  secrecy  as  possible,  and  but  little  has  been  pub- 
lished that  would  enable  the  average  chemist  to  pass 
judgment  on  the  different  grades  and  varieties  of  var- 
nish, and  for  this  reason  a  short  discussion  of  some  of 
the  principal  classes  of  varnish  may  not  be  amiss. 

583.  Floor  varnishes.     Goods  of  this  class  should  have 
a  medium  consistency.     If  heavy  they  will  require  a 
longer  time  to  dry  and  harden  than  is  desirable,  and 
would  be  apt  to  become  marred  from  usage  before 
thoroughly  hardened;   if  too  thin  they  will  not  afford 
the  desired  protection  to  the  wood.     In  price  they  are 
about  the  same  as  for  first-class  interior  varnishes, 
ranging  usually  from  $2.00  to  $2.50  per  gallon  whole- 
sale.    Floor  varnishes  are  usually  "long  oil"  goods,  as 
a  high  degree  of  elasticity  is  required. 

584.  Interior  varnishes.     Varnishes  for  interior  work 
should  be  of  fairly  heavy  consistency,  so  as  to  stand 
rubbing.     For  the  best  class  of  work  they  should  be 
"long  oil,"  although  "short  oil"  goods  may  be  used 
for  the  undercoats.     In  price  they  usually  range  from 
$2.00  to  $2.50  per  gallon  wholesale.     Often,  especially 
in  contract  work,   "No.   1   Coach"  goods  are  used. 
This  term  means  absolutely  nothing,  as  it  stands  for 
no  specific  grade  or  quality  of  varnish.     Sold  under 
this  name  varnishes  are  put  on  the  market  for  $0.90  to 
$1.10  per  gallon,  or  even  less,  and  are  usually  high  in 
rosin    and    benzine    or    heavier    petroleum-products. 
Polishing  varnishes,  such  as  are  used  for  pianos,  high- 
class  furniture,  etc.,  are  usually  of  excellent  quality, 


276  PAINT  AND  VARNISH  PRODUCTS. 

averaging  in  price  from  $2.50  to  $2.75,  although  the 
very  best  grades  may  run  as  high  as  $3.50  whole- 
sale. 

585.  Interior  varnishes  being  subjected  to  less  stren- 
uous usage   than   floor  finishes,   carriage   or  exterior 
goods,  the  tendency  has  been  to  lower  the  standard  of 
quality,   until  perhaps  low-grade,  inferior   goods  are 
the  rule,  and  really  high-grade  finishes  the  exception, 
on  the  market  at  the  present  time.     Neither  is  the 
size  of  the  company  any  guarantee  that  the  product  is 
of  high  value,  for  many  of  the  best  grades  of  varnishes 
are  made  by  small  concerns  who  depend  on  the  quality 
of  their  goods  rather  than  on  extensive  advertising  for 
their  sales. 

586.  Exterior   varnishes.     These    should    always    be 
"long  oil"  goods.     Spar  varnishes,  which  are  the  usual 
type  of  exterior  varnishes,  should  be  of  medium  con- 
sistency, tough  and  elastic,  and  not  easily  scratched. 
In  price  they  usually  range  from  $3.00  to  $3.75  per 
gallon  wholesale.     Carriage  varnishes  bring  the  high- 
est price  of  all  varnishes,  and  their  successful  manu- 
facture is  accomplished  by  only  a  comparatively  small 
number  of  concerns,  and  but  few  domestic  brands  are 
rated    equal    to    the    best    imported    English    goods. 
Domestic  carriage  varnishes  range  from  $4.75  to  $5.75 
wholesale,  and  the  best  imported  English  goods  at  about 
$7.25  per  gallon. 

587.  Short   volume.      It   is   a   lamentable   fact   that 
varnish  manufacturers  almost  invariably  defraud  the 
consumer  by  putting  out  their  packages  short  in  vol- 
ume.    Of  eleven  samples  purchased  by  the  author  on 
the  open  market,  in  the  original  package  none  were 
full  measure.     The  amount  of  shortage  is  given  in  the 
following  table: 


THE  PRACTICAL  TESTING   OF  VARNISHES.        277 


No. 

Description. 

Per  Cent  Short- 
age of  Contents. 

1 

Floor  Varnish              

3  2 

2 

Floor  Varnish      

4  2 

3 

Floor  Varnish      

2  1 

4 

Interior  Varnish  

3  2 

5 

Exterior  Varnish     

2.1 

6 

Coach  Varnish 

2  1 

7 

Interior  Varnish 

8  4 

8 

Floor  Varnish 

3  2 

9 

Exterior  Varnish                              

4  2 

16 

Floor  Varnish              

9  5 

18 

Floor  Varnish          

13  3 

Average     

5  0 

Five  per  cent  shortage  in  measure  represents  a  very 
fair  profit  to  the  manufacturer  in  itself. 

588.  Significance  of  lime  in  varnishes.     The  addition 
of  five  to  six  per  cent  of  quicklime  to  melted  rosin 
makes  it  considerably  harder.     The  compound  formed 
easily  dissolves  in  linseed  oil  (at  the  present  time  wood 
oil  is  largely  used),  and  when  properly  thinned  forms 
the  base  of  about  all  the  cheap  varnishes  on  the  market. 
Such  varnishes  are  characterized  by  giving  a  brilliant 
surface,  easily  scratched,  and  in  a  short  time  liable  to 
crack  badly.     The  relation  between  the  percentage  of 
lime  (CaO)  in  the  varnish  and  its  toughness  and  elas- 
ticity is  not  marked  enough  to  enable  the  chemist  to 
pass   judgment    on   its   working    qualities    from   the 
amount  of  lime  it  contains. 

589.  Sixteen  of  the  leading  varnishes  on  the  market 
were  tested  out  for  toughness  and  elasticity,  and  then 
the  amount  of  calcium  oxide  determined  in  each,  the 
results  obtained  being  given  in  the  following  table. 


278 


PAINT  AND  VARNISH  PRODUCTS. 


No. 

Kind. 

Per  Cent  of 
Calcium  Oxide 
in  Varnish. 

Elasticity  and 
Toughness. 

2 

Floor  Varnish  

0.868 

Good 

3 

Floor  Varnish  

0.246 

Good 

4 
5 
6 

7 

Interior  Varnish  
Exterior  and  Interior  Varnish 
No.  1  Coach  Varnish  .... 
Interior  

0.200 
0.178 
0.313 
0  195 

Good 
Medium 
Good 
Poor 

9 
11 
13 

Exterior  
No.  1  Coach  Varnish  
Interior  Varnish  

6.265 
0.271 

Medium 
Poor 
Very  Poor 

14 
15 
17 
19 
21 

Interior  Varnish  
Coach  Varnish  
Interior  Varnish  ....... 
Interior  Varnish  
Interior  Varnish  

0.161 
0.800 
0.158 
0.158 
0.212 

Poor 
Medium 
Medium 
Good 
Good 

23 
25 

Interior  Coach  Varnish  .  .  . 
Interior  Varnish  .... 

0.532 
0.281 

Poor 
Poor 

590.  Of  twelve  brands  of  floor  varnishes  examined  by 
the  author,  four  were  altogether  too  thin  for  the  pur- 
pose intended;  and  of  fourteen  interior  finishes,  four 
were  exceedingly  thin,  and  several  of  the  remainder 
were  below  average  in  this  respect. 

Of  a  total  of  twenty-six  of  the  leading  brands  of 
floor,  exterior  and  interior  varnishes  tested  out  by 
the  author,  seven  were  considered  first  class  in  all 
respects,  eight  were  medium  or  just  fair  quality,  while 
eleven  were  unquestionably  poor  and  inferior  both  as 
regards  working  and  the  quality  of  the  film  after  dry- 
ing. Of  the  above  eleven,  eight  were  interior  finishes. 

591.  The  twenty-six  with  but  two  exceptions  flashed 
at  room  temperature,  a  fact  which  is  worthy  of  consid- 
erable attention  on  the  part  of  the  consuming  public 
as  regards  fire  risk. 


CHAPTER   XXXIII. 

VARNISH   STAINS  AND   COLOR  VARNISHES. 

592.  Varnish  Stains.  Such  data  as  may  be  obtained 
from  an  analysis  of  varnish  stains  is  only  of  limited 
value  as  they  are  essentially  varnishes  carrying  a  small 
percentage  of  very  finely  ground  colors,  such  as  C.  P. 
chrome  green,  sienna-red  toner,  etc.  The  moderate 
price  at  which  these  goods  are  offered,  preclude  the  use 
of  high-priced  varnishes,  and  in  order  to  obtain  the 
desired  effect  usually  a  blend  of  two  or  more  varnishes 
is  used.  Some  of  the  most  successful  varnish  stains 
are  prepared  by  blending  a  straight  China-wood-oil 
rosin  varnish  with  a  short-oil  kauri-rosin  (two-thirds 
low-priced  kauri,  one-third  W.  W.  hardened  rosin)  var- 
nish. Dark  oak,  light  oak  and  walnut  shades  are  ob- 
tained by  adding  sufficient  asphalt um-rosin  varnish  to 
produce  the  desired  effect ;  mahogany  and  rosewood  by 
using  a  red  toner  in  connection  with  the  asphaltum 
black;  light  and  deep  cherry  with  raw  sienna  and  red 
toner  and  the  various  greens  with  C.  P.  chrome  green 
and  small  amounts  of  the  asphaltum  black. 

These  goods  have  been  widely  advertised  during  the 
last  few  years  under  .various  designations  of  which  the 
word  "  lac  "  usually  forms  a  part.  The  prevailing  tend- 
ency has  been  to  use  inferior  rosin  varnishes  which 
are  not  only  brittle  but  scratch  easily,  showing  the 
customary  " rosin  streak/'  A  better  class  of  goods 
can  be  prepared  by  adding  a  long-oil  kauri  or  manila 
varnish  to  give  elasticity. 

279 


280  PAINT  AND  VARNISH  PRODUCTS. 

593.  Color  Varnishes.     The  varnish  stains,  above  de- 
scribed, possess  two  defects,  they  do  not  give  clear, 
transparent  effects  owing  to  the  fact  that  the  pigments 
themselves  are  opaque.     Also  these  pigments  settle  out 
on  standing  and  more  or  less  trouble  is  experienced  in 
bringing  them  into  uniform  suspension  when  desired 
for  use.     These  difficulties  have  been  overcome  by  the 
use  of  colors  soluble  in  the  varnish  such  as  the  "fat 
colors,"  so  called,  and  certain  organic  lakes.     These 
afford  a  clean,  transparent  effect,  and  are  easy  to  apply 
but  they  lack  permanency  of  color.    They  are,  however, 
widely  used. 

594.  Stain  Finishes.     These  finishes  are  designed  to 
be  applied  over  furniture  or  any  interior  finish,  which 
has  already  been  fully  varnished,  in  order  to  give  a 
mission,  Flemish,  Antwerp  or  similiar  effect.     In  other 
words  the  stain,  in  a  measure,  sinks  into  the  already 
applied  varnish.     These  stains  are  prepared  by  dis- 
solving various  "fat  colors,"  such  as  fat  black,  fat  yel- 
low, fat  orange,  fat  red,  fat  brown,  etc.,  in  a  combina- 
tion of  benzole,  naphtha  or  petroleum  spirits,  and  a 
long-oil  varnish.     These  fat  colors  can  be  secured  from 
any  of  the  leading  color  supply  houses  and  are  aniline 
colors  combined  with  a  fatty  acid,  like  oleic  or  stearic 
acid  and  sometimes  rosin.     While  satisfactory  to  a 
certain  extent,  these  finishes  are  not  very  durable, 
scratches  showing  badly  because  the  color  of  the  surface 
of  the  wood  has  not  been  changed. 

595.  Oil-wood  Stains.     This   class  of   goods  is  very 
similiar  to  varnish  stains,  except  that  in  this  case  the 
varnish  is  replaced  by  linseed  oil.     As  found  on  the 
market  they  will  contain  15  to  25  per  cent  of  a  light- 
colored  boiled  oil,  and  the  balance  naphtha  or  petroleum 
spirits,  except  for  the  small  amount  of  pigment  present. 


VARNISH  STAINS  AND  COLOR  VARNISHES.       281 

The  following  analyses  are  characteristic  of  this  class 

of  goods. 

i.  ii.  in. 

Green,  Cherry,         Dark  Oak, 

per  cent.  per  cent.          per  cent. 

Linseed  oil  .                                                 14.. 0  16.4  18.0 

Naphtha 79.0  77.4  75.0 

Chrome  green 7.0  

Red  toner 6.2             

Asphaltum  varnish 7.  Ol 

100.0  100.0  100.0 

1  Obtained  by  comparison. 

Some  manufacturers  use  a  mixture  of  boiled  and  raw 
oil  in  order  to  regulate  the  drying.  The  separation  of 
pigment  and  vehicle  is  best  effected  in  a  centrifuge. 


CHAPTER   XXXIV. 

ENAMELS  AND   VARNISH   SPECIALTIES. 

596.  Valuation.  The  essential  consideration  in  the 
analyses  of  enamels,  enamel  finishes  and  varnish  paints 
is  the  nature  or  composition  of  the  vehicle  which  is 
largely  varnish.  The  pigments  that  may  be  present  in 
the  above  classes  of  products  are  of  comparatively  little 
moment  as  their  analysis  and  duplication  are  exceed- 
ingly easy.  The  vehicle,  on  the  other  hand,  offers  many 
difficulties  as  it  is  usually  prepared  by  the  blending  of 
two,  three  or  even  four  varnishes  of  very  diverse  com- 
positions and  characteristics.  The  result  being  that 
the  blend  thus  obtained  behaves  very  differently  as  re- 
gards flowing,  drying,  toughness,  hardness,  etc.,  from 
the  component  varnishes.  These  variations  in  be- 
havior often  take  unexpected  directions,  as  for  example, 
two  varnishes  each  of  which  may  be  comparatively  slow 
in  drying,  will,  when  mixed,  dry  quickly.  It  is,  therefore, 
not  possible  for  an  analysis,  even  if  exact,  of  a  varnish 
to  show  anything  of  value  as  regards  the  physical  or 
working  qualities.  It  will,  however,  serve  to  give  an 
approximate  idea  of  the  cost  of  the  materials  used,  and 
at  about  what  price  the  varnish  in  question  could  be 
duplicated.  Having  this  information  at  hand,  and  a 
suitable  variety  of  varnishes  of  known  composition  and 
properties  to  work  with,  it  is  not  a  difficult  matter  for 
an  experienced  chemist  to  very  closely  duplicate  the 
various  specialty  products  on  the  market.  If  the  three 
requisite  conditions  above  enumerated  are  not  ob- 

282 


ENAMELS  AND  VARNISH  SPECIALTIES.  283 

tained  the  value  of  any  results  that  may  be  secured 
will  be  extremely  uncertain. 

597.  Adoption  of  Analytical  Methods.     Recently  con- 
siderable progress  has  been  made  in  the  valuation  of 
varnish  products  by  analysis  and  practically  every  var- 
nish chemist  has  his  own  scheme  which  depends  for  its 
success  very  largely  on  intuition,  judgment  and  the 
closeness  with  which  he  keeps  in  touch  with  the  varnish 
industry.    It  is,  therefore,  difficult,  if  not  impossible,  to 
outline  a  scheme  in  print  that  can  be  followed  and  in- 
telligent results  obtained.     The  outline  suggested  by 
Dr.  Mcllhiney,1  if  worked  over  carefully  by  the  chemist 
himself  on  varnish  products  of  known  composition,  will 
establish  certain  relative  standards  which  together  with 
his  own  judgment  and  intuition  will  enable  him  to  de- 
termine approximately  the  composition. 

598.  Mcllhiney's  Method.     The  oils  and  gums  may 
be  examined  by  Mcllhiney's  scheme  as  follows: 

"The  process,  which  is  here  described,  depends  upon 
the  fact  that  although  the  union  between  oil  and  hard 
gum  is  too  intimate  to  be  broken  up  by  the  selective 
solvent  action  of  any  solvent  acting  directly  upon  the 
original  mixture,  the  combination  may  be  broken  up 
and  the  oil  and  gum  brought  back  to  more  nearly  their 
condition,  before  they  were  melted  together,  by  sub- 
mitting the  mixture  to  the  action  of  caustic  potash  in 
alcoholic  solution  and  subsequently  acidifying  the  solu- 
tion of  potash  salts  so  formed.  By  this  means  there 
is  obtained  from  hard-gum  varnishes  a  quantity  of  gum 
insoluble  in  petrolic  ether  very  closely  approximating 
the  amount  of  hard  gum  actually  existing  in  the  var- 
nishes, while  the  linseed  oil  is  represented  by  its  fatty 
acids  which  are  readily  soluble  in  this  solvent  unless 

1  Proceedings,  Am.  Soc.  for  Testing  Materials,  1908. 


284  PAINT  AND  VARNISH  PRODUCTS. 

they  have  been  oxidized,  in  which  case  some  of  the 
fatty  acids  of  the  linseed  oil  will  accompany  the  insol- 
uble hard  gum. 

"In  carrying  out  the  method  an  opportunity  is  given 
to  determine  not  only  the  weight  of  the  oil  and  of  gum, 
but  also  the  Koettstorfer  figure  and  the  percentage  of 
glycerin  in  the  mixture.  All  these  data  taken  together 
give  a  basis  for  corroborating  the  main  figures. 

599.  "The  process  is  carried  out  by  weighing  into  an 
Erlenmeyer  flask  2  to  10  grams  of  the  varnish,  adding  a 
considerable  excess  of  approximately  half -normal  solu- 
tion of  caustic  soda  or  caustic  potash  in  very  strong  or 
absolute  alcohol,  distilling  off  the  major  portion  of  the 
solvent,  and  redissolving  in  neutral  absolute  alcohol. 
The  solution  is  then  titrated  with  a  solution  of  pure 
acetic  acid  in  absolute  alcohol,  approximately  half-nor- 
mal strength,  to  determine  the  amount  of  the  excess  of 
alkali  present.  From  this  the  Koettstorfer  figure  is  de- 
termined as  the  exact  strengths  of  the  acid  and  alkali 
solutions  have  been  ascertained  independently  by  com-  * 
parison  with  known  standards.  A  further  quantity  of 
the  standard  solution  of  acid  in  alcohol  is  added  so  as 
to  exactly  neutralize  the  total  amount  of  alkali  originally 
added.  By  this  means  the  acid  bodies  liberated  from" 
their  combinations  with  alkali  are  obtained  in  solution 
in  strong  alcohol.  To  this  solution  there  is  now  added 
a  sufficient  quantity  of  petrolic  ether  to  dissolve  the  oil 
acids  and  this  petrolic  ether,  being  miscible  with  the 
strong  alcohol,  forms  with  it  a  homogeneous  liquid. 
Water  is  now  added  to  the  mixture  in  such  .amount  as 
to  so  dilute  the  alcohol  contained  that  it  is  no  longer  a 
solvent  for  fatty  or  resin  acids;  this  addition  of  water 
causes  the  petrolic  ether  which  was  mixed  with  the  alco- 
holic liquid  to  separate,  carrying  with  it  the  fatty  acids. 


ENAMELS  AND  VARNISH  SPECIALTIES.  285 

The  rosin  goes  with  the  fatty  acids  while  the  hard  gum, 
being  insoluble  in  either  the  petrolic  ether  or  in  the  very 
dilute  alcohol,  separates  in  the  solid  state.  The  aque- 
ous and  ethereal  layers  are  now  separated  in  a  sepa- 
rating funnel  and  each  is  washed,  the  watery  layer  with 
petrolic  ether  and  the  petrolic-ether  layer  with  water. 
The  petrolic-ether  layer  is  now  transferred  to  a  weighed 
flask,  the  solvent  distilled  off  and"  the  residue  of  fatty 
acids  and  common  rosin  weighed.  This  latter  is  then 
examined  further  by  Twitchell's  method  to  determine 
the  amount  of  rosin  which  it  contains,  or  it  may  be  ex- 
amined qualitatively  in  a  number  of  ways  to  establish 
its  identity. 

600.  "The  aqueous  layer  is  freed  from  the  suspended 
hard  gum  which  it  contains  by  filtering,  and  from  any 
further  quantity  of  gum  which  the  weak  alcohol  may 
have  retained  in  solution  by  evaporating  off  the  alcohol 
and  again  filtering.     The  remaining  aqueous  liquid 
contains  the  glycerin  and  this  is  determined  by  the 
Hehner    method    with    potassium    bichromate  —  the 
method  ordinarily  used  for  examining  spent  soap  lyes. 

601.  "The  hard  gum  is  according  to  this  plan  pre- 
cipitated in  such  a  way  that  it  adheres  to  the  sides  of 
the  glass  vessel  in  which  the  alcohol  and  petrolic-ether 
mixture  is  diluted  with  water;   the  easiest  method  to 
weigh  it  is,  therefore,  to  carry  on  the  operation  of  dilu- 
tion in  a  weighed  glass  vessel  and  then  to  dry  and  weigh 
the  hard  gum  in  this  vessel.     It  frequently  happens 
that  some  of  the  hard  gum  cannot  be  conveniently 
retained  in  this  vessel  but  that  it  must  be  filtered  out  on 
a  weighed  filter  and  the  weight  so  found  added  to  that 
of  the  main  portion. 

602.  "If  the  varnish  contains  non- volatile  petroleum 
or  other  unsaponifiable  matter  it  will  naturally  be  in- 


286  PAINT  AND  VARNISH  PRODUCTS. 

eluded  in  the  fatty  and  resin  acids,  and  it  would  be 
necessary  to  saponify  the  latter  and  extract  the  un- 
saponifiable  matter  from  them  while  in  the  alkaline 
state;  this  operation  is  so  familiar  to  chemists  that  it 
is  mentioned  here  only  to  call  attention  to  the  necessity 
for  it  in  some  cases. 

603.  "It  would  naturally  be  expected  that  on  ac- 
count of  the  well-known  insolubility  of   the  oxidized 
fatty  acids  in  petrolic  ether,  some  of  the  acids  of  the 
linseed  oil  which  had  been  polymerized  by  heat  during 
the  cooking  of  the  varnish,  or  which  had  been  oxidized 
during  the  blowing  process  to  which  some  linseed  oil  is 
subjected  before  making  it  up  into  varnish,  would  fail 
to  dissolve  and  would  be  counted  in  with  the  hard  gum 
instead  of  with  the  linseed  oil.     It  appears  as  a  matter 
of  fact  that  this  source  of  error  is  of  slight  importance 
in  the  case  of  oil  thickened  by  heat  but  that  the  blow- 
ing process  gives  an  oil  which  is  not  completely  ac- 
counted for  by  the  soluble  fatty  acids  recovered.     This 
difficulty  may  be  largely  overcome  by  taking  advantage 
of  the  greater  solubility  of  the  oxidized  fatty  acids  in 
alcohol  as  compared  with  the  hard  gum;    the  freshly 
precipitated   gum   contaminated   with   oxidized   fatty 
acids  is  treated  with  a  moderate  quantity  of  cold  alco- 
hol of  about  85  per  cent  and  allowed  to  digest  for  some 
time.     The  soluble  matter  so  extracted  is  then  recov- 
ered separately  by  evaporating  off  the  alcohol. 

604.  "  Rosin  when  present  is  usually  combined  with 
lime  in  the  proportion  of  about  1  part  of  lime  to  20  parts 
of  rosin.     An  examination  of  the  mineral  constituents 
of  the  varnish  is,  therefore,  of  some  value.     The  extrac- 
tion of  the  mineral  bases  may  be  effected  by  treating  a 
quantity  of  the  varnish,  somewhat  thinned  with  ben- 
zine, with  strong  hydrochloric  acid,  and  examining  the 
aqueous  liquid. 


ENAMELS  AND  VARNISH  SPECIALTIES.  287 

605.  "The  amount  of  fatty  acids  obtained  repre- 
sents about  92.5  per  cent  of  the  linseed  oil.  The  identi- 
fication of  these  fatty  acids  as  belonging  to  linseed  oil 
or  to  china  wood  oil  may  be  satisfactorily  accomplished 
in  some  cases,  but  there  are  undoubtedly  many  var- 
nishes in  which  the  analyst  will  be  unable  to  identify 
and  determine  the  oils.  The  odor  and  physical  char- 
acteristics of  the  recovered  gum  are  quite  as  important 
as  the  known  chemical  tests  of  which  the  acidity  and 
the  Koettstorfer  figure  are  among  the  most  important." 


INDEX. 

A.  PAGE 

Acetic  acid  in  white  lead 99 

Adulteration  of  turpentine 59 

Aldehyde  free  alcohol 37 

Agricultural  paints 229 

Aluminum  silicate 86 

Analysis  of  black  pigments 185 

Analysis  of  calcium  carbonate  pigments 82 

Analysis  of  Chinese  blue 206 

Analysis  of  iron  oxides 175 

Analysis  of  leaded  zincs 122 

Analysis  of  petroleum  thinners 75 

Analysis  of  Prussian  blue 204 

Analysis  of  shellac  varnish , 255 

Analysis  of  white  lead 92 

Analysis  of  white  paints 143 

Analysis  of  zinc  pigments ; 107 

Antimony  vermilion 220 

Asphaltum  varnish 268 

B. 

Barium  carbonate 79 

Barium  sulphate 77 

Barn  paint 237 

Barrel  paste 229 

Borax 21 

Bromine  value  of  oils 44 

C. 

Calcium  carbonate 80 

Calcium  sulphate 84 

Carbon  dioxide 97 

Caustic  soda 20 

China  wood  oil 31 

Chloride  of  lime 20 

Chrome  yellow 211 

Classification  of  varnishes 275 

289 


290  INDEX. 

PAGE 

Cobalt  blue 210 

Cold-water  paints 167 

Combination  emulsifiers 21 

Composition  of  colored  paints 170 

Corn  oil 28 

Cottonseed  oil . 27 

Covered  testers 54 

Crack  and  crevice  fillers 234 

D. 

Damar  varnish 255 

Detection  of  water  in  paints " 11 

Dipping  paints 232 

E. 

Enamels 282 

Emulsions 17 

Estimation  of  arsenic  and  antimony 117 

Estimation  of  lead Ill 

Estimation  of  mineral  oil 25 

Estimation  of  petroleum  products 52 

Estimation  of  rosin  oil , 45 

Estimation  of  water 12,  14 

Estimation  of  wood  alcohol 250 

Excessive  use  of  volatile  oils 57 

Evaporation  test 46 

F. 

Fineness  of  pigments . 124 

Fire  test 56 

Fish  oil ' 28 

Flash  point 38 

Flat  wall  finishes 138 

Free  fatty  acids 36 

Functions  of  turpentine 32 

G. 

Geer's  modification 67 

Gravity  of  pigments 127 

H. 

Heavy  turpentine 68 

Hexabromide  test 47 


INDEX.  291 

!•  PAGE 

Inert  pigments 77 

Iodine  number 32 

Iodine  number  of  oils 35 

Iron  fillers 234 

J. 

Japans  and  driers 239 

K. 

Kalsomine 163 

Koettstorf er  number 36 

L. 

Labeling  paint  products 1 

Lakes 165 

Linseed  oil  constants 32 

Linseed  oil  foots 41 

Linseed  oil  specifications 47 

Litharge » 222 

Lithopone 122 

Long  oil  varnish 262 

M. 

Magnesium  silicate 86 

Metallic  lead 94 

O. 

Oil  from  inferior  seed 39 

Oil  reductions 137 

Oil  varnishes 257 

Oleate  of  lead 19 

Orange  mineral 221 

Op'en  testers 56 

P. 

Paris  white 80 

Paste  wood  filler 91 

Petroleum  thinners 72 

Practical  testing  of  varnish 269 

Practical  testing  of  paint • 129 

Priming  enamels 229 

Priming  ochres , 182 

Prussian  blue .  .  204 


292  INDEX. 

R-  PAGE 

Ratio  of  pigment  to  vehicle 10 

Red  lead 221 

Rosin  oil 29 

Rough  stuff 234 

S. 

Sandy  lead 93 

Saponification  value 36 

Separation  of  mineral  oil 26 

Separation  of  vehicle 5 

Separation  of  volatile  oils %. 23 

Shade  cloth  paint 229 

Shellac 245 

Shellac  varnish 247 

Shingle  stain 236 

Short  oil  varnish 261 

Silica 87 

Soya-bean  oil 30 

Specific  gravity 24 

Spot  test 24 

T. 

Thermometer  correction 139 

Tinting  strength 126 

Turpentine. 19,  59,  60,  62 

Turpentine  reductions 138 

Typical  analysis  of  mixed  paints 157 

U. 

Uniform  sample 4 

Use  of  centrifuge 6 

V. 

Varnish  stains 279 

Vermilion 211 

Vermilion  primer 229 

W. 

Whiting 80 

Wood  fillers 223 

Wood  turpentine 63,  64,  67 

Zinc  sulphate 110 

Zinc  white  .  ,                                                                                 116 


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